Is the foam from the bucket seat different from one year to another?

I want to know if the foam padding change between year?

I have what I think to be 73-74 bucket seat and a 72 rear seat in my 71 Duster....
I need to change the seat cover, but my foam is in good condition.
I like the 72 look and was wondering if the foam was the same and if only the cover was different.

I know the general shape is the same, but the foam make a difference?