Hola The sales booklet for 63 has the belts listed as a dealer installed item. If you should remove the head-liner you will not find a hard spot for a shoulder hook up. When you remove the rear seat you will be able to install a set of rear belts at any location that you want to drill a hole. My front seat belts where in the car when we got it. The rear seat belts are from a 67 Chrysler 300. Both belts appear to be of the same design. Rodger & Gabby 47 De Soto Custom 63 Le Baron 66 Le Baron