I'd put in some aftermarket seats of era correct appearance before I shelled out those bux.

You can buy a pair of brand new seats in era appearing trim from Speedway for less than those Legendary seat covers.

All new seats, new foam, new springs, new frame, including tracks. No 50+ year old foam, tracks, frames, springs etc you still have to "fix" after you cough up for the covers.

https://www.speedwaymotors.com/Low-Back-Vinyl-Bucket-Seat-Passenger-Side-Black-w-Seat-Mount,491573.html

or

https://www.speedwaymotors.com/Pro-90-Series-Bucket-Seat-Passenger-Side-Black-with-Seat-Mount,491566.html

Are they a direct fit? Nope, you will most likely need to mod the supplied tracks.

Will they be "correct"? Nope, but I am not a resto guy either.

And if you want to step up to a more supportive seat that might not be 100% era appearing, well here you go. Just a hair more than the covers

https://www.speedwaymotors.com/Procar-Rally-Series-Seat-Passenger-w-Frame-Slider-Mount,485331.html