Jesper, from what I know many archives including rules and classifications are no more avalaible. I do remember a separated grid but it was for Production car races. I agree that with several 1600 cars, Golf/Audi 80 and Corolla, a separated classification would make sense. I had a go for you here, but nothing appears at least prior to the 90's, sorry(you must add Circuit to the search):
https://www.ffsa.org/univers/circuit...its/classement