I know R2 has strictures on what it can afford to do - proper GN spec wheels and tires seem to be a bridge too far in pre-90s era NASCAR.
Guessing that what is in the kit was there from the first of the downsized "G" body GM NASCAR series - Dave Van can speak to that better than I can.
Anywhoo...the PPP wheel and tire sets are much better and as noted either here or on FB, getting that stance right is everything with these cars.