However, after the war, a self-taught engineer, pilot, and auto racer, Ben F. Gregory, conceived a mini-jeep design and built a successful prototype, later named the "MM-100".

No carmaker was interested in his car, but he was inspired to use some of its design features, such as leading- and trailing-arms suspension, in a more modern four-wheel drive off-road vehicle, or jeep, and he found additional investors willing to fund a prototype.

Joining on 1 January 1953 as project manager, Crist brought with him three of the main people who had worked on the original Bantam vehicle: Chet Hempfling, Ralph Turner, and Frank McMillan.

Attempts were made to substitute the Lycoming O-145, an American aircraft engine, but it was deemed too expensive and difficult to adapt to a ground vehicle.

[7] There was a competing prototype built by Willys, the 1953 Bobcat or "Aero Jeep", which was to share as many parts as possible with the M38 and M38A1 to save costs.

[9] In April 1958, AMC and the USMC executed a contract for delivery of 250 production M422 vehicles contingent upon successful trials of the first seven.

[13] Also, this was the first U.S. small military vehicle designed with independent suspension all around (front: leading arms/trailing arms rear), sprung by ¼-elliptical leaf springs.

The air-cooled 107.8 cu in (1.8 L) developed 52 bhp (39 kW) and 90 lb⋅ft (122 N⋅m) of torque, which propelled the vehicle to a top speed of 65 miles per hour (105 km/h), with a 55-mile-per-hour (89 km/h) military rating.

Instead, the two additional seats are integrated into the functional tailgate, and two small folding backrests are placed on the top of the rear fenders.

Other features included USMC lifting rings and holders in front of the fenders to store aluminum water cans.

Like other Marine Corps contract vehicles, the M422s came from the factory with all deep-water fording equipment installed, except for the pipes.

After production of 1,045 units, the Mighty Mite evolved into the M422A1, 6 inches (152 mm) longer in both wheelbase and overall length, as well as 80 pounds (36 kg) heavier.

Once put into production, the longer wheelbase model was designated the M422A1 and featured a reinforcing rib on the rear fender forward of the wheel opening.

When the M422 debuted, it coincided with the adoption of helicopters like the Bell UH-1 "Huey" with much more carrying capacity than the Marine Corps' Sikorsky HRS with its 2,650-pound (1,202 kg) cargo limit (including crew and fuel), for which the M422 had been developed.