I must admit that I usually group stuff like gassers, awb, 2% cars, f/x cars, ss/s, etc... all together. To me it was more of a time period thing, I don't think the sanctioning bodies were consistent with their nomenclature either. In reading the SS-Drag Racing the F/Sedan book, it sounds like these classifications were changed at will sometimes
Bottom line, why does it matter? It's a cool old car, call it whatever ya like. I'd like to see a match race between the '65 I-beam Chevelle vs. the '66 I-beam Nova
