Check out the current CCR and Atlanta Region ITO/ITU rules at the link provided by Tom Sprecher in post #2 above (I'd repeat the link but I'm pretty much computer illiterate). A true SPO car (tube frame, slicks, no limit to cubic dollars spent) would obviously totally outclass any car based on a production platform, which is why we wanted to provide ITO/ITU for guys that have modified their "street" cars beyond what is allowed in the ITCS.