75 Plymouth Duster

I have a feeling that in 1975, the floor was slightly revised for catalytic converter clearance. The converter generates heat so it might be possible that there was a hump in the floor to allow some room around it. The frame rails are the same. Very few people would put a stock single exhaust and catalytic converter back in the car so I'd guess that the earlier floor pans would work. Also, the firewall and floorpan below the rear seat are similar so it is possible that only the middle sections are different.