Modifying the seat back from a coupe frame was fairly straight forward; there is a rigid wire that defines the depth of the coup seat. In a 'vert it's pinched to join the rear. otherwise, the seat components are assembled essentially the same, just more narrow. I had to make my own rear seat as well, but I didn't had the ability to make the bottom curve in more than the coupe, so I had to buy one. Keep in mind you at least have the 64-68 frames to choose from... not that will make it any easier...