Front bench seat foam questions

Hopefully someone can help me with this. I am purchasing a front bench seat with split backs for my 71 Demon project. I have searched and searched and can not locate a source for the seat foam. Was the frame on these molded into the foam? Anyone know where I can locate replacements? I've checked Legendary and the other known sources. I would prefer to buy ready made foam rather than trust the upholstery shop to custom make it. I'm hoping to have the seat within the next few days and will be able to ascertain the construction then. I'm buying a 71 Dart as a parts car for $800 because it has the seat and a couple other things I need. As always.... any and all help is appreciated.

Thanks!