1966 Grumman Kurbmaster Cummins Swap: The NEMO Arms Battlewagon

Is The NEMO Arms Battlewagon The Ultimate Diesel Conversion?

Last reviewed: April 2026

It’s not every day that you come across a fully trickedout delivery truck that’s been equipped to hold enough heavy artillery to make any Second Amendment activist or postapocalyptic zombie survivor wet his pants. Though it looks battle ready, the initial idea behind this vehicle started out very much unlike what you see on these pages.

It was first conceived when Clint Walker noticed how frequent and troublesome trips to the firing range had become. Clint is the vice president of NEMO Arms, a leading manufacturer of precision longrange ARtype rifles, including the world’s first .300 Win Mag AR and U.S. Military Tier ONE operations.

He quickly came to the realization that making 45-minute trips to the range to test new products would be easier with a proper vehicle to haul them in along with all of the tools and supplies he would need.

Why a 1966 Grumman Kurbmaster?

At first, Clint decided it was time to step things up by purchasing a mailtype truck that could be modified to hold the company’s product. Since he wasn’t too familiar with these types of vehicles, he gave his old friend Jeff Davy of Devious Customs a ring to look at options for his new project.

From there, Jeff searched around and found this 1966 Grumman Kurbmaster that was very local to his Riverside, California based shop.

After a short trip to go check it out, he ended up taking it for a reasonable offer and hauling it away in order to get the ball rolling.

With missing floor sections and a transplanted Cummins-powered drivetrain, this truck was already a work in progress that was in need of some love. Since Clint used to write for a few automotive magazines in the past, he’d become familiar with the lowered truck scene.

So, instead of just fixing the newly acquired delivery truck, he decided that he wanted to let Jeff have his fun with it and fully deck it out. From there, Jeff and his crew, including Jeff Johnson and Nathanial Dray, started the disassembly of this sizable beast.

Frame-Off Chassis Rebuild: Air-Bag Suspension on a Kurbmaster

First thing on the list of modifications was to plant the ride flat on the pavement. Like most vehicles, this truck and its chassis were never designed to sit shockingly low.

To handle this task, the Devious crew dropped the frame from under the body and created a new one out of 2×8-inch steel tubing and a front clip salvaged from a 1989 Chevy Suburban.

Front suspension, a new set of control arms was fabricated and a pair of Western Chassis dropped spindles was attached. Then a pair of 3,200-pound ContiTech air bags was mounted, while the sway bar was adapted to the adjustable suspension.

Rear suspension, a parallel four-link and Watts link keep the rearend from a Dodge 2500 truck in place. A rear cantilever linkage was made to lift the truck up with the use of a matching set of air bags. Helping to keep this truck from tipping over on the road is a torsion style sway bar made to fit the rear.

Once the chassis was complete, the floor was closed up with 18-gauge aluminum sheet metal and received a durable coating of Line-X. Sealed off, the dash was made functional with the addition of a few gauges and AccuAir eLevel and iLevel controllers for the air suspension.

Custom Interior & NEMO Arms Showcase

It’s now drivable with the use of a Flaming River steering column complete with a black anodized Draft steering wheel from Billet Specialties, and a custom foot pedal assembly also helps out in this de- partment.

For looks and added comfort a pair of air-equipped seats from Bostrom were added. Because this thing needs to be a complete rolling arsenal it was loaded with a plethora of NEMO Arms products that are displayed throughout the vehicle.

To make sure they are always in good working order a workbench from Tough Country was fitted in as well as a stainless toolbox.

Exterior: Flat Black, LED, and “Liberal Repellant”

This truck is one bad mother, and to get the point across, the exterior was toughened up with a few styling cues.

This includes the rugged bumpers custom made by Tough Country and the numerous Plashlight LED lights that were wired by Ryan Parma and Aaron Dunway to lead the way in the dark and offer target sighting for nighttime shooting.

Finishing it off is a flat black paint job that was laid down by Matt Hutcheson Designs, who then airbrushed the logos and Second Amendment sayings throughout.

In its complete form it has already made a big impression at both the SEMA show and SHOT show, and now it’s on the road for many other events. Not only does it have the look, but the NEMO Battlewagon is also ready for a serious throwdown. Let’s just hope no liberals get in its way.

Clint would like to thank Jeff Davy and his crew at Devious Customs and also all of the brothers and sisters serving at the tip of the spear that give up their freedoms so that we may sleep peacefully at night. DW

Build Specifications

ENGINE

• 5.9L Cummins 12-valve
• Custom serpentine kit
• Custom intake tubing with K&N 8-inch filter
• Custom 4-inch straight pipe exhaust
• Painless wire harness
• 47rh automatic transmission
• B&M pistol-grip shifter
• Push-button overdrive
• Two-piece driveshaft
• Dodge 2500 rearend
• Custom 20-gallon aluminum fuel cell

SUSPENSION

• 1989 Chevy Suburban front clip
• 3/4 frame made from 2×8- inch steel tubing
• Custom front control arms with uniballs
• Western Chassis dropped spindles
• Modified front sway bar
• Parallel four-link
• Rear-mounted cantilever links
• Watts link
• Torsion sway bar in rear
• 3,200-pound Contitech air bags
• Fox racing shocks
• Accuair E-Level air bags
• Oasis XD 3000 compressor
• Chevy 3500 truck Hydroboost

WHEELS & TIRES

• 20×10-inch Moto Metal MO956
• 245/55 20 Nitto Terra Grappler

INTERIOR

• Leather-covered Bostrom seats
• Aluminum sheet metal work covered in Line-X
• Custom-built dash
• Classic Instruments gauges
• Flaming River steering column
• Billet Specialties Draft black anodized steering wheel
• Custom foot pedal assembly
• Universal Vintage Air kit
• Tough Country workbench
• Stainless toolbox
• Custom display racks
• JVC 7-inch navigation head unit
• JL Audio marine speakers, subwoofers and amplifiers
• Kinetik 2400 batteries and Intelligent Power Supply
• R-Blox sound deadening

Frequently Asked Questions

What engine is in the NEMO Arms Battlewagon?

The Battlewagon runs a 5.9L Cummins 12-valve diesel paired with a 47RH automatic transmission. The 12-valve was chosen for its mechanical simplicity, bulletproof reliability, and strong torque output — well-suited to the heavy Kurbmaster step van body.

Who built the NEMO Arms Battlewagon?

The build was executed by Jeff Davy and his crew — including Jeff Johnson and Nathanial Dray — at Devious Customs in Riverside, California. NEMO Arms VP Clint Walker commissioned and directed the project.

What is a Grumman Kurbmaster?

The Grumman Kurbmaster is a walk-in step van originally manufactured by Grumman Allied Industries, widely used by the U.S. Postal Service and commercial delivery fleets from the 1960s through the 1980s. Its tall, spacious body makes it a popular platform for custom conversions, food trucks, and specialty vehicles.

Where has the NEMO Battlewagon been shown?

The Battlewagon has appeared at SEMA (Specialty Equipment Market Association show) in Las Vegas and the SHOT Show, and continues to make appearances at industry and enthusiast events across the country.

What does NEMO Arms make?

NEMO Arms is a precision rifle manufacturer based in the United States, best known for building the world’s first AR-platform rifle chambered in .300 Winchester Magnum. Their rifles are used by civilian shooters and U.S. Military Tier ONE operators.