No, the front seat won't fold forward so someone can get into the back seat. And the back seat(bottom seat) in a 4 door has square corners and the seat goes strait back, the 2 door has a round front corners and narrows back in somewhat on the back side of the seat(bottom seat)You would need to retro fit the frame of the seat from a 4 door car and then have it covered!
The sedan has a bench seat in the front. The coupe has a split back bench seat to allow access into the rear seat. It is possible that the rear seats will match up, but a '57 Bel Air has so many pecker tracks back there that you may just want to get it completely reupholstered.