Pretty much everything in regards to the foam...Shape is different,listing{attaching}wires are incorrect to fasten the older upholstery...I went through this years ago...Here's a pic of a set I did for a 73 RR these seats are nothing like the 71-72s...I've had a few sets of custom upholstery made up when Legendary still did that service and I always needed to start with the correct cores...