I've got a '65 that I installed the deluxe front retractable seat belts in. It came with front seat belts so I just used the original mounting nuts that were already welded in and used the same bolt that came off the original belts to install the retractors and the buckle end. There was no provision for rear seat belts at least that I could find. Below is a link to a couple of pictures. I'm not sure if this will help or not.