Seat cover swap

I bought a set of bucket seats at monster mopar last weekend, their out of a 75 or 76 dart sport or duster, I looked at the legendary website. Anyway, they will eventually make their way into my 73 swinger and I would like to know weather or not the seat foam was the same for the 73's as for the 75/76. I would like to have somewhat correct looking seats in my car, They dont offer any other color beside black and white for those years plus the stitching is different. From what I can tell of the seats the covers have their own foam backing which gives it its design. So if the foam is the same I can just put 73 covers on them, right? Anybody?