The M3A1 Light Tank was a significant incremental improvement over the earlier M3 Light design program begun originally in 1940. Focusing on increased crew safety and survivability, the Al model also incorporated improvements that increased the operational accuracy and lethality of the vehicle when fielded against enemy tanks of equal weight and class. Many of the design improvements incorporated into the M3A1 went on to become international standards for armor design to this day. Production of the M3A1 began in May of 1942 and continued through February of '43. Of the nearly 20,000 Stuarts of all classes and types built during the war, production of the M3A1 totaled 4,621 units. Of this number 4,410 were powered by the Continental W-970-9A seven-cylinder. 262 hp. radial gas engine. The balance of this total being powered by the Guiberson T-1020-4 nine cylinder, 250 hp, radial die-sel engine. Both these engines utilized a 5-speed syncromesh transmission and the vehicle could attain a top speed on firm ground of 36 to 38 mph. Dimensions for the M3A1 were as follows: Length 173 inches, Width 88 inches and a Height of 100 inches. Total vehicle weight in combat ready condition was 28,500 pounds. Internal fuel storage was a mere 54 US gallons. This gave an affective range without auxiliary external fuel tanks of approximately 70 miles for the gasoline radial and slightly more with the diesel radial. The problem of limited internal fuel storage was to plague the Stuart design throughout its entire service life.