Check Pontiac Fiero's - my recollection is that they are very narrow.

High back seats look odd in these cars.

Also - but not low buck, look at one of Glide Engineering's offerings - and what I'm using in my '31 Roadster is the 50-50, but their Universal might fit.

By the way, once you pay for re upholstery, repairs and any mods to the frame, you might just be equal cost wise to a good after market seat