I've run dog dish caps on my '64 GTO with the original 14" wheels, factory 15" wheels and now 17" bare steel wheels from Wheel Vintiques (through Summit).
Summit listing for 5x5 15" wheels - I think that's what you're looking for.
https://www.summitracing.com/search/...ques-62-series
I'm very happy with my 17's by WV.