my chapter of scca allows the following in the "stock" classes: adjustable dampers, any stock size wheels, catback exhaust systems, cai and sri intakes, short throw shifters, and any tire you want, including slicks. where they draw the line (as far as suspension mods go) for the jump from a stock class to a street touring or street prepared class would be things like: bigger sways, strut tower bars, larger than stock wheels, any additional chassis stiffening, lowering/stiffer springs, and coilovers. things like that. your rules may very well be different though.