Hi just wanted to get some basic info as I am new to racing and don't want to screw up too badly. I purchased a BMW Z3 that was originally built by TC Kline for SSB competition. I am converting to ITA because of age 96. My question is in the GCR under Z3 for SSB class the SSR Integral wheel is considered a stock piece at 16x8.5". However in IT the maximum is 7" wide. Why would a "stock" item as defined by the GCR for a "stock" class not be allowed to run in another class?