30 x 9 max tire size. And if you run Stock pistons, parts etc it will likely be an index car. There is a list of NHRA approved replacement parts... pistons, heads- casting #'s etc.... There is alot of technology (=$$$$$$) that goes into these "stock" engines. Everything is massaged and blueprinted. There is a tolerance for all specs and they need to be checked and lots of machine work needed to be competitive.

Get a rulebook and get reday to get into the minutiae of every part on the car. Alot of work but Very Very rewarding. My uncle ran stock and super stock until he died, now my cousin has taken over and I help out when I can.