Formula cars are as allowed by the Monoposto Register rules: thru 1963 for Formula Jr., pre-1976 Formula V as long as they meet the pre-1969 rules, pre-1970 for Formula B, Formula C, and Formula II, pre-1973 for Formula Ford, 1973 thru 1981 for Club Ford, and thru 1966 for Formula 1.

At certain events, SOVREN allows an EXHIBITION class for distinctive racing automobiles which are too new to fit in the above categories but were produced before Dec 31, 1989 such as Formula 1, Can-Am, Trans-Am, Indy cars, etc.