Group 1A - 1955-1961 Sports Racing Cars under 2000cc RaceGroup 2A - 1973-1982 IMSA GT, GTX, AAGT Cars RaceGroup 3A – 1955-1961 Sports Racing Cars over 2000ccGroup 4A – Bugatti Grand Prix CarsGroup 4B – 1955-1962 GT CarsGroup 5A - 1964-1969 FIA Mfg. Championship Cars RaceGroup 5B - 1961-1966 GT Cars under 2500ccGroup 6B – 1959-1975 Grand National Stock Cars drum brakesGroup 7a Trans AmGroup 7B - 1963-1966 GT Cars over 2500ccGroup 8A - 1970-1976 FIA Mfg. Championship Cars RaceGroup 8B - 1959-1966 Sports Racing CarsGroup 9B – 1966-1983 F-1 Cars