For the 1972-1975 period, the FIA Group 2 and 4 rules were in force. A maximum capacity of 5000 cc was valid for the early period, just as in the ETCC. In 1976, Germany did not fell like moving over to Group 5; instead they prolonged the old rules for one more year (albeit with 1976 tyre sizes and weight rules), but allowing 1976-group 2 and 4 cars into the field , which did not make any sense - with one exception.
Frank de Jong
Amsterdam, the Netherlands