I hear you on the quality thing! It is difficult to find someone that makes good reproduction 73/74 parts. With that said, Palco has door panels and seat backs that appear to be much better the Accuform, theirs are just terrible, and Metroparts is now making seat backs that are suppose to be much better than anybody.
Regarding the seat foam, the buttons on the 73/74 attach to a rod that lays on top of the seat foam, which should have a channel, this rod on correct seat covers goes into a sleeve that is attached to the seat covers. Legedary has the correct ones and they use heavier material as well. I will be sending my cheap covers back and going with Legendary, plus they are doing my upper panels and i would like those to at least match the seats.
I find it interesting that my seat buns are not co-mingled/molded with the wire frame, they appear to just slip over the frame. Maybe the PG ones are correct for my seats. I need new ones, as my frames have rust, which is all over the foam. No sense in putting new seat covers on top of rusty foam!