I have a set of bucket seats out of a 73 duster that I am going to recover. Does anyone know if I can use a set of 70 duster seat covers and put them on the 73 seats, with the 73 seat foam?
I did a similar thing you are asking only I had a set of 75 Valiant seats and put 74 Duster covers on them and they fit O.K. but are not the best. I would say you need to get the right bucket seat foam to fit what you want or you will have to modify them to fit right. It will not be a perfect fit right off the bat.
The 75 Valiant seats that I had were covered with red velour fabric and had a different pattern than the 74 Duster vinyl, maybe that's why they didn't fit so well.