no question in ITS the body and bumper have to be stock as Ed said. IT is after all a restrictive prep class. now cars that exceed the prep rules can normally run in ITE in most places (or ITEZ where available) but you may have another problem with tech. the safety standards in IT are based on the crush structure of the original car being intact. with limited cages (compared to prod or GT) and stock fuel tanks tech may be reluctant to issue a logbook with out the protection of bumpers.