In playing with a bunch of 67-72 Valiants this summer I found that the backs are the same but the bottoms are different. The bottoms on all of my post cars are the same as the 4 doors. Took a nice set out a 72 4 door and put them in a 68 post and they fit great. I would assume that Dodge would be the same but it has been a long time since I played with a Dart post. And lets not add Duster seats to the mix.