I once tried to mount my buddies 28x10.5 hoosiers on a 8.5 inch rim, it didn't rub on the inside but it came real close to the lip of the quarter panel. If i pushed down on the rear bumper it would contact the tire. Wouldn' be a good idea to take it to the track like that, seeing how the rearend squats when it launches. Stiff springs or massaging the lip might solve the problem, assuming you have the correct back spacing. now i'm running 26x10 mt's, but i hear that 28x9 fits well also. Probably shouldn't use tubes unless you plan on using rim screws, i don't run tubes.
george