I think its a bit more ambiguous than the muscle car era --- then quite literally, --- there was an arms race between Chrysler, GM and Ford every year -- flexing their muscle with increasingly bigger and more powerful creations across the range ---

--- and then --- poof -- 1974 happened --- Corvette got plastic bumpers, the Mustang turned into something weird, the big blocks were neutered - and the era was just ........... gone

The muscle car era was also pretty short , starting in 1964 with 389 GTO's and ending in 1973 with SD455 Firebirds

With bicycles -- I named my '00 Waterford track machine as being a Classic, if not vintage yet, --- but its counterpart from 1945 or so, a Paramount trackie, - is both classic and vintage --- so its covering a whole bunch more years than something like the muscle car era