^^ A lot happened in the hot rod aftermarket world between the 60’s and 80’s. I also am thinking somebody put an older windshield in a newer glass body. But we might never know if the OP doesn’t come back.
It wouldn’t surprise me if Ford Duplicators made a few coupe bodies way back then, decided that they didn’t sell as well as roadsters and were harder to build so they didn’t pursue it any further.