Those oval bumpers are a new one to me. It's been a lot of years since I replaced my original, smashed down, seat bumpers but I don't remember the originals being anything different from the repro round one I replaced them with. I do know there were not two per seat back.
I researched some Camaro and other GM late 60's and found the two different seat bumpers. There was a round and oval types, part numbers 4406843 and 7712535 but I could not tell which went with what cars or seat types. (Bucket vs bench? Standard vs custom? Or something else?) Good question.
