This 1979 Chevy K10 Has A Wicked 12-Valve Cummins And 2.5-Ton Rockwell Axles

We heard it before we ever laid eyes on it. That unmistakable sound of a 12-valve Cummins turbodiesel. What made it stop us in our tracks was the fact that it was not coming from a Dodge. Instead, Forrest Roth’s diesel-swapped 1979 Chevy K10 rolled into view. The Cummins swap caught our attention, but the rest of the build backs it up with a purpose-built chassis, triangulated four-link suspension, coilovers, and massive Rockwell 2.5-ton axles.

Heavily Modified Cummins, Beefed 47RE Transmission

The heart of this K10 came from a 1996 Dodge 3500 that Forrest bought strictly as a donor. From there, the 12-valve Cummins was torn down and rebuilt to produce, and handle, serious power. Inside, it runs marine pistons, an upgraded camshaft, and larger injectors. Airflow and fueling are pushed further with a 63/67mm turbocharger, a modified P-pump, and an AirDog lift pump, while ARP hardware keeps everything clamped tight under pressure.

The valvetrain is reinforced with Hamilton Cams tappets and an Industrial Injection tappet cover, along with 4,000-rpm governor springs and 60-pound valve springs. A pair of Optima YellowTop batteries sit tucked under the cab between the framerails, and a five-inch exhaust handles the job of clearing out spent gases.

47RE, SCS Gearbox

Backing the Cummins is a 47RE four-speed automatic that has been completely reworked by Firepunk Diesel to survive four-digit horsepower levels. Firepunk’s Anteater STC system replaces the factory PCM and allows full control over shift strategy. From there, power is routed through an SCS Gearbox 12-inch-drop unit with a 1:1 ratio before heading to the axles.

2.5-Ton Rockwells With Disc Brakes, 4.90:1 Gears, And More

The axles are as serious as the engine. The Rockwell 2.5-ton axles were sourced from C&C Equipment in Nashville, Indiana, and then upgraded across the board. Each axle is fitted with disc brakes powered by a hydroboost system, along with a pinion brake for added control. Inside, Ouverson Engineering 4.90:1 gears help put the Cummins torque to work.

The front axle was narrowed by 7.5 inches and outfitted with manual lockout hubs from Boyce Equipment. Steering duties are handled by a custom hydraulic crossover system paired with RedHead steering gears. Out back, the hubs were flipped inward to further tighten the overall width.

Remote-Reservoir Coilovers, Triangulated Four-Link, 44s

The suspension setup is a beast like the engine and axles. A triangulated four-link system constructed from 0.250-inch-wall DOM tubing keeps everything planted. Big Shocks remote-reservoir coilovers provide 16 inches of travel and feature adjustable top mounts for dialing in performance.

That suspension clears beefy rubber. The truck rides on 19.5/44-20LT Interco Super Swamper TSL Bogger tires wrapped around 14-inch-wide aluminum wheels built by Real Racing Wheels.

Custom Chassis

The backbone of the build is a custom frame. Forrest started with Chevy longbed framerails, shortened them, boxed the structure, and added 2.5 inches of height so a body lift was not needed. Strength comes from crossmembers built with 2×4- and 2×6-inch steel.

A hand-fabricated drop subframe sits below, supporting the SCS gearbox and serving as the central mounting point for the suspension links.

Interior And Exterior Bits

Inside, the truck blends old-school style with upgraded components. A Squarebody Syndicate steering column and gauges bring updated functionality, while Corbeau seats and a center console sourced from a 2016 Chevy truck improve comfort and usability.

On the outside, a Warn Enforcer front bumper adds protection, and custom aluminum emblems on the front fenders give the truck a subtle personal touch.

In The Family Since 1979

This K10 is more than a diesel swap project. It has been in Forrest’s family since new. His grandfather bought it in 1979 and used it for plowing snow. Later, it passed to his father, and eventually to Forrest when he turned 16 in 1998. It served as his daily driver through high school.

Over time, the truck has gone through multiple transformations, with the latest rebuild completed in 2021. The result is what you see here today. A family heirloom turned Cummins-powered machine that delivers both history and horsepower in equal measure.