Homegrown 1978 High Boy Ford Cummins Swap

A Barn-Built, Body-Swapped ’78 Ford Packing A 700HP Cummins

Far from the 330,000-mile Cummins that once powered the truck, Jared Jones sourced a 24-valve block and built this 5.9L from the ground up. Not only was the block machined to accept larger 14mm main studs and head studs, but it was fire-ringed as well. A stock crank swings a set of factory forged-steel 12-valve rods that I’ve been shot-peened and fitted with ARP rod bolts. Other additions include a Scheid Diesel street cam, along with the company’s billet tappet cover, front cover, and intake plate. A set of 4130 Chromoly push tubes from Trend Performance and 165-lb Hamilton valve springs complete the 5.9L valvetrain upgrades.

The original engine’s 160hp P7100 was worked over and benched at Scheid Diesel. It sports 5,000-rpm governor springs, 191 delivery valves, and flows 470cc’s of fuel. It also features 22 degrees of timing advance and forces fuel through .093 lines. A set of SAC style, 5×0.013 Scheid injectors handle in-cylinder fuel delivery while a stock lift pump—equipped with a stiffer, Comp Cams inner valve spring—feeds ample fuel to the low-pressure side of the P7100 at any rpm. Also, notice the Scheid billet front cover here.

Through the passenger side fender well you can spot the atmosphere turbo in Jared’s setup. The BorgWarner S400 sports a cast 75mm compressor wheel, a 96mm turbine, and a T6 inlet, 1.10 A/R exhaust housing. After converting to an HX40 flange, which reduced the turbo’s outlet to 4-inches, drivability improved tremendously. In fact, Jared reports that despite the engine’s healthy fueling the S300/S400 combination makes for a very responsive and clean-burning truck.

No, it’s not a High Boy. It just happens to look like one—and we’ll dare say it’s better than any all-original dent side. It’s a ’78 Ford body fastened to a second-gen Dodge frame, suspension, and axles, and it’s got a well-fueled and compound turbocharged 12-valve Cummins under the hood. It also happens to belong to Jared Jones, driver of one of the fastest oil burners in existence, the Scheid Diesel dragster. As a diesel technician at Scheid, you could say Jared knows a thing or two about a B-series Cummins, along with how well the ’94-’02 Dodge chassis holds up to high horsepower. In combining his ’94 Ram with his uncle’s old F-100, he built a vehicle any truck guy would envy.

An Idea Is Born

Following a lengthy period of spirited street driving, boosted four-wheel drive launches, and beating up on Corvettes and Camaros in his 500hp regular cab ’94 Dodge, Jared snapped the input shaft in the truck’s 47RH. With the Ram out of commission, he grabbed the keys to his uncle’s two-wheel drive ’78 F-100. Then, after the Ford’s C4 automatic gave up a year or so later, Jared had a “wait a minute” moment one night. With the two broken down trucks parked side by side, he noticed the wheelbase of the second-gen was close to the F-100’s. After measuring, the wheels started turning and Jared began to kick around the idea of swapping the Ford body onto the Dodge chassis.

A set of quick-lighting compounds begins with a 57mm S300 positioned on the engine’s T3 Steed Speed exhaust manifold and on top of an S475 atmosphere charger. Jared fabbed up all intercooler piping using sections of exhaust that were originally intended for a Power Stroke. The 3.5-inch diameter hot and cold-side tubing connects to a flipped ’94 intercooler. Turbo drain tube kits (for both the S300 and S400) and low profile shock mounts from Fleece Performance Engineering helped make installation of the compound arrangement as seamless as possible.

As a way of tying the B-series Cummins in with the Ford, it powers, Jared, tracked down the valve cover you see here and installed it above cylinder number 1. Finding this Ford badge usually means you’re looking at a 5.9L under the hood of a ’92-’98 Ford school bus.

With the wheelbase of the second-gen and F-100 being so close in length, the frame isn’t cut or shortened in any way. However, the boxed ¾-ton Dodge frame is considerably stronger in every way. As can be seen here, the ’94 Ram 2500’s front coil springs were retained, as were the factory leaf springs in the rear.

Despite the truck being finished and made road-worthy more than 12 years ago, Jared still adds something new each winter, when—in an effort to keep it as far away from road salt as possible—its daily driving duties are brought to a halt. In the future, Jared plans to buy another Dodge frame and completely redo the build, and he’s even thinking about trading in its Patina for fresh paint.

What followed was the piecing together of a one-of-a-kind Fummins using the parts he had available to him, and sourcing everything else either from the junkyard or the aftermarket. “I didn’t start out with a High Boy, I just used what I had,” he told us. “I didn’t have a lift so I bought an A-frame at the scrap yard, the wife and I got started pulling the body off the Dodge.” Due to the difference in frames, mounting the cab and dog house on the second-gen chassis called for 2.5-inches of body lift. Aside from that, the process of swapping the body over proved pretty straightforward.

Subscribe Our Weekly Newsletter

From A Split-Block To A Brand-New B-Series

Two years after Jared’s creation became road-worthy, the 330,000-mile 12-valve that’d been raced, beaten, and regularly exposed to 2,000-degree EGT in its previous life split the block. Its replacement would be based on a 24-valve crankcase, which Jared had machined to accept fire rings, 14mm main studs, and 14mm head studs (which were donated courtesy of the Scheid dragster engine). The fresh 5.9L also features ARP fasteners throughout, including the rod bolts that fasten shot-peened factory rods to the stock crank. A Scheid street cam, Trend Performance push tubes, and 165-lb Hamilton valve springs sum up the valvetrain upgrades.

Putting his days of drag racing the truck behind him, Jared traded his 47RH automatic for this ’05 model year NV5600 manual. The six-speed benefits from a McLeod Racing street twin clutch and, thanks to changing out the input hub, mates to the ’94 Ram’s NP241 transfer case. With the rugged and reliable hand-shaker in the mix, a lot less transmission-related breakage has been experienced, and Jared tells us the truck returns a very respectable 21-22 mpg on the highway.

After killing the original Dana 70, Jared purchased a replacement with a Yukon Gear & Axle gearset present, and the 3.54-geared rear axle has proven rock-solid thus far. To quell axle wrap, Jared has a set of CalTracs on the shelf waiting to be installed. The truck’s conventional exit exhaust system is void of a tip and measures 4-inches from the turbo back.

The truck’s B Series emblems are another repurposed factory badging item that just seems to “fit.” Pulled from a ’95 B series Ford school bus, they’re right at home on Jared’s 6BT-powered blue oval.

Benched P7100 And 5x13s

Long gone are the days of Jared’s P7100 being set up to support a docile 160 hp. With a trip over to Scheid’s pump shop, the ’94 model year P-pump was made to flow 470cc of fuel while retaining optimum street manners. It’s been graced with 5,000-rpm governor springs, and 191 delivery valves, and is set at 22 degrees of timing. Downwind of the pump are six SAC-style, Scheid-built injectors equipped with 5×0.013-inch nozzles. An OEM Cummins lift pump supports the P-pump, but in order to maintain fuel supply at high rpm its inner valve spring was upgraded with a replacement spring from Comp Cams.

In the cab, a rear bench seat out of a first-generation crew cab Super Duty sits in place of the factory bench. Ford fans well-versed in the dent side era of trucks will also spot the factory radio delete bezel present in the dash, a fairly rare option.

Street And Tow-Friendly Compounds

After the first Cummins, a well-fueled single turbo 12-valve that’d allowed the truck to make 500 to 550 hp at the wheels, Jared decided to run compounds with the new 5.9L. Now, the truck is considerably more streetable and he spends a lot less time watching the pyrometer. The quick-spooling combo begins with a 57mm S300 mounted on a T3 Steed Speed exhaust manifold. An S475/96/1.10-atmosphere turbo contributes 35 psi of boost at full tilt. Jared fabricated the 3.5-inch diameter intercooler piping that routes boost to and from a factory ’94 Dodge intercooler, and a Scheid billet-aluminum intake plate sits in place of the stock piece.

The steering column serves as the mounting point for four Auto Meter gauges: a 5,000-rpm tach, a 2,000-degree pyrometer, a 60-psi boost pressure gauge, and a 100-psi boost gauge. Jared keeps tabs on coolant temp, oil pressure, and voltage by way of three Sport-Comp II series analog units mounted beneath the ashtray.

NV5600 Swap

Between the costs and hassle associated with fixing broken 47RH parts and knowing a third-gen owner who was looking to swap an automatic in place of his NV5600, Jared decided to pull the trigger on a manual conversion. A twin disc street clutch from McLeod Racing sits on the input shaft of the ’05 model year six-speed. On the opposite end rests an NP241 transfer case, which was part of the original drivetrain equipment on Jared’s ’94 Dodge. The only change required to accommodate the NP241 was an input hub swap. Cruising in overdrive (sixth gear), Jared’s Ford returns as much as 22-mpg on the highway.

One Of One

It all started with a tape measure, and now Jared always has the coolest truck in the parking lot. Whether it’s from the rattle of the 12-valve Cummins, the sweet whine produced by the well-spec compound arrangement, or the simple fact that it’s a High Boy-era Ford out cruising around in the year 2022, Jared’s one-of-one creation has endless attention-grabbing power. When he tossed us the keys, we promptly fired it up, jammed a few gears, and moved it to a more photo-friendly location. Thirty minutes later, we’d already lost count of all the raised thumbs and complements thrown our way.

Also helping to complete the look of the old Ford is a dual front steering stabilizer. Sourced from Skyjacker Suspensions, Jared tells us it was installed for cosmetic appeal above all else, although we’re sure it keeps bump steer and wheel vibration at bay.

If you want a High Boy-era Ford to look the part, you install a set of Slots. The 17×10-inch, 8 on 6.5-inch US Mags wheels are wrapped with 305/65R17 Cooper Discoverer S/T tread. The iconic wheels, combined with the 33-inch all-terrains they ride on, fit the bill perfectly—and effectively trap the truck in time.

In a world overflowing with brand-new, $80,000 pickups, Jared’s trapped-in-time Ford is a welcome change of pace. It combines the iconic, old-school looks of the ’73-’79 F-series line with the ruggedness of a second-gen Dodge chassis—and a 700hp P-pumped Cummins backed by a manual transmission doesn’t hurt matters, either. But most importantly, it can’t be bought.