I used a cube van as a camper/race car hauler. Granted its a small race car...
I had the floor built over the wheel arches + beaver-tailed from the arch back. I had long oak ramps and a winch (superwinch-with a cordless remote which I HIGHLY recommend.) I was able to use the roll up door-but I always had a wet dream of making a light weight flip up door that would act as an awning (I always had an Ez-up set up). The front of the box was a small living area. Using bigger bus you should have plenty of options.
Put up some pics of your race car! Former drag racer here (bikes) but still work in the trade.