Prior to 1966, the FIA's Group 4 classification applied to Sports Cars which were in compliance with FIA Appendix C regulations. It also included recognised Series Touring Cars, Improved Touring Cars and Grand Touring Cars which had been modified beyond the respective Group 1, Group 2 or Group 3 regulations under which they had been
homologated. Beginning with 1966, an overhaul of FIA categories saw Group 4 Sports Cars redefined such that they were now subject to a minimum production requirement of 50 units in 12 consecutive months and had to be fitted with all equipment necessary for use on public roads. A 5000cc engine capacity limit was applied for 1968 and the minimum production requirement was reduced to 25 units for the 1969 season. For 1969,
Appendix J of the FIA International Sporting Code defined groups for
Touring cars,
Grand Touring cars and
Sports cars as follows: (numbers between brackets are required minimum production in 12 consecutive months). • Group 1: series-production touring cars (5,000) • Group 2: touring cars (1,000) • Group 3: grand touring cars (500) • Group 4: sports cars (25) • Group 5: special touring cars •
Group 6: prototype-sports cars For 1970, the limited production sports car category was renamed from Group 4 to
Group 5 and, in the same year, Group 4 became the class for special grand touring cars with minimum production of 500 in 12 consecutive months For 1971, the relevant FIA classifications were as follows: == Sports car racing ==