Here is a list of the WWII General Motors War Material Production 1940-45: (This is the best list I could assemble from the contemporary sources at war's end)
198,000 Diesel engines for tanks & landing craft
206,000 Airplane engines
13,000 Complete bombers and fighter planes
97,000 Aircraft propellors
301,000 Aircraft gyroscopes
38,000 Tanks, tank destroyers and armored vehicles
854,000 Trucks, including amhibious DUKWs
190,000 Cannons
1,900,000 Machine guns and submachine guns
3,142,000 Carbines
3,826,000 Electric motors
11,111,000 Fuses
360,000,000 Ball and roller bearings
119,562,000 Shells
39,181,000 Cartridge cases
540,619,000 Grand Total
To this day, the government has not forgotten GM's contribution.
1942, Production Goes to War - Generations of GM