As usual,,, the rules got changed, yet again, to cater for things like RX7's, to be classified as a Touring Car.
Another little anomaly, was a certain model Alfa aromeo 105, and a certain Porsche 911, were, in late 1960's/early 1970's, given Touring Car status.
Now today, that same model, of both, is allowed in both Historic Sports Cars, ( Group S) and, Historic Touring Cars, ( Group N)