Hi Philip Kelly
I don't know if you are aware of it, but 3dsMax does actually ship whit a large amount of 3d-cars: Some quite OK models from AXYZ-design and some very low-poly models from another company. They all comes as part of Civil View, and can also be found in the 3dsMax Samples package. When accessed through Civil View then can be animated with rotating wheels and can be assigned various colors.
This is what I primarily use myself. Hope it helps :)