Nothing really. You may have to drill a hole or two for the metal sail panels but like the others stated about the cardboard headliner versus the cloth one. You may have to drill holes for the bows too to put a cloth head liner in. In addition you will have to go with 70/72 doors also due to the style being different, different size interior panels and such. This can be done but will require some work but for you this should be a walk in the park from the other stuff you are doing to your car!!
Chas.