Z06's can compete in SCCA Pro Solo, National Tour, Divisional, Regional and Local competition. Most compete in 3 classes
Super Stock - a very limited preperation stock class in which mods are generally limited to safety items.
A Street prepared - Street licensed and driven cars prepared to higher tolerences. SCCA T1 prepared cars can also compete here
Street Modified 2 - Heavily modified street drivern cars with some limitations.
You should alway consult the CURRENT SCCA Solo Rule Book, Sportscar "Fastrac" updates and proposed rule changes and the SCCA GCR's (General Competition Rules Rule Book).
SCCA Solo I and SCCA T1, Club Racing, GT-1, Pro Racing, and World Challenge rules are included in the GCR's and othe publications
The following charts are a quick references for those preparing cars for SCCA Solo II (Autocross) events. They may not be up to date.
http://www.sff.net/people/dburkhead/prepcompare.htm
http://www.moutons.org/sccasolo/Rules/stock.html
http://www.moutons.org/sccasolo/Rules/index.html