Stock class for SCCA autocross allows *ANY* DOT-approved tire that fits the oem sized wheel that is not on the exclusion list.

stock on my car is 195/50/15 front and 205/50/15 rear. I run a 205/50/15 front and a 225/50/15 rear for competition purposes this year. Sometimes I run a 225/45/15 in the rear also.