Good to know....

I suppose you could buy rear bench or 2 from a parts yard at a reasonable price. Rob the foam and have your upholstery guy cut it to fit.
Our classic seats have springs like household furniture. That relieves some of the pressure on the foam and make them more comfortable. New seats are just dense foam over steel frames, no springs. They shape contours into them along with adjustable to make them more comfortable.
I too bought skins and foams from Legendary, 67 B'cuda buckets, but it was 8 or 12 years ago, I forget. I dont like raised side bolsters so didn't add them. I'm happy with them. I can't imagine I'll drive it enough to wear out the seat foam.