to carry off-road, while all other standard GI 1/4 ton vehicles (even the M151) were rated at . And if needed, there was even a version of the M416 trailer specially adapted for towing by an M422: the M416B1. Like other Marine Corps contract vehicles, the M422s came from the factory with all deep-water fording equipment installed, except for the pipes. In its early development stage the Marines developed a lightweight flotation kit that could easily be stored on the M442 when not in need, in which four large tubes inflated by exhaust encompassed the bottom part of the frame that allowed the vehicle to swim deeper waters. The vehicle's spinning wheels provided propulsion and steering in the water. In 1958, seven prototypes passed grueling tests, and the first 250 vehicles were built by American Motors. These units went into mass production in 1960 and AMC built 3,922 Mighty Mites through 1962 for the U.S. Marine Corps. Over the years, the vehicle was produced in two model versions: the M422 and M422A1. The M422 had a tiny wheelbase. After production of 1,045 units, the Mighty Mite evolved into the M422A1, six inches (152 mm) longer in both wheelbase and length, and heavier. The first Mighty Mites to have the 71" wheelbase were an experimental model fashioned from an M422. They had an extended, frame and aluminum added behind the seat and crudely fashioned tool storage boxes. This model was the M422E1 of which only a few were made. Once put into production the 71" wheelbase model was designated the M422A1. Either model could be fitted with rear-mounted spare tire and a sturdier windshield similar to the Willys M38A1 that, along with top bows, would facilitate the use of a canvas winter top. The addition of the rear-mounted spare tire rendered the tailgate unusable. At over US$5,000 per unit, it was relatively expensive, and by the time the Mite went into full production, the military's helicopters had become so much more powerful that the vehicle quickly became obsolete. The Marine Corps' Sikorsky H-19 with its cargo limit (including crew and fuel), for which the M422 had been developed, was being superseded by the Vietnam era UH-1 “Huey", that could carry more than 1½ times that load. These factors may account for the small production total, as well as the short production time period. See also Crosley Farm-O-Road, a 1950 jeep-like utility