The letter refers to the classification that the car would have fallen under when drag racing. Such as Altered, Altered Wheelbase Fuel Injected, Carburated... etc. One of the old timers will probably post up a list of all the designations and their exact meaning. The number was just the car's race number. In DoS, I think the 32c is more for looks, though the 32 stands for 1932, and the 'c' probably stands for carburated.