The M54 5-ton 6×6 Cargo truck (G744) was the basic cargo model of the M39 Series truck. Rushed into production by International Harvester in 1951, soon Kaiser (renamed Kaiser-Jeep in 1963) also became a major manufacturer, with Diamond T and Mack building smaller numbers. It was designed to transport a 10,000 lb, 14 ft long cargo load off-road in all weather. In on-road service the load weight was doubled.The M54 was the primary heavy cargo truck of the U.S. Army and U.S. Marine forces during the Vietnam War, and was also used by the U.S. Navy, U.S. Air Force, and ARVN forces. The M39 series were originally powered by a Continental R6602 engine, a 602 cu in (9.9 L) overhead valve inline 6 cylinder gasoline engine developing 224 hp (167 kW) at 2800 rpm. The -A1 upgrade had a Mack ENDT-673, a 673 cu in (11.0 L) turbocharged inline 6 cylinder diesel engine developing 210 hp (160 kW) at 2100 rpm. The -A2 upgrade had a Continental LDS-465-1A, a 478 cu in (7.8 L) turbocharged inline 6 cylinder developing 175 hp (130 kW) at 2100 rpm. The M39 Series began to be replaced by the M939 Series in 1982. The M39 weighted in at 19,945 lb and had a range of 280 mi with a top speed of 52 mph.