64-66 cuda fold down seat into 63-66 dart

Has anyone used the rear seat from a 64-66 barracuda in a 63-66 dart? I see where the seat back has a relief in the middle and it looks like the sides have a narrow bit towards the bottom. Thought it might be interesting to have the fold down seat in my 66 Dart. I already have the barracuda / valiant front bucket seats and I saw a nice condition matching rear seat from a barracuda not too far where I live.
Why?