I wouldn't call me a hero till I prove I can do anything remotely associated with 3D modelling, lol
My ideas are basically this:
Make #1: 1940s Modified, since the majority of the cars raced were Fords, I figure one model would cover half the field, so that would allow a plethora of options with that. Not only that, but this would also double for the possibility of some pre-war carsets, provided someone were up to the challenge of finding documentation/photos from that far back. I've only seen a few in Fielden's books.
Make #2: Late 1940s Olds. Going by my research, this was one of the more prevalent models throughout the first Strictly Stock season. The main issue with making a late 40s mod is that there was literally no rhyme or reason when it came to brand uniformity. It was race what you brung, and that's gonna be an issue. My solution would probably be figure out what were the most numerous models run, or go for the most iconic.
Make #3: The Nash Ambassador was a pretty unique model that could double (with the proper template) for some of the other models at the time that featured a sloped back design.
Make #4: Any of these would do most likely.