71 Demon Seats?

Hi, I am restoring my 71 340 Demon and need seats...Guy before me put 73 seats and a fold down back seat??? and yes I know the fold down seat is not functional. He welded brackets in and had it set it in the down position...Anyway two questions...

First, I located a 72 demon back seat and need to know if it is the same frame just a different pattern or is the foam also different???

Second, are E-body front seats the same frames just different seat tracks or are they totally different??

Thanks,

Also, I have a very nice set of 73 front seats that I would be willing to trade plus $ for a set of 71 seats...They are white but, would need a recover...