1957 -1966 Ford trucks
1958 -1972 Chevy trucks
60's-70's Dodge trucks
For the trucks they could make many of the bed options for all three makes. Like a parts pack ,Wrecker, Box, flat bed, utility box, camper and on and on.
The G-body GMs would be a great selling kit platform. with all the different makes on one frame and drive train it should cut the price for the molds .