On a '55 Courier, the factory originally installed 1/8" thick sheets of masonite for the side-wall panelling. The masonite was exposed and had no upholstery. These were Mainline series cars for utility/delivery use, so luxury was in short supply on these. On my car, the old masonite was still there, so I used the old panels to cut out new 1/8" lauan plywood, stained and polyurethane coated. I also used the old panels to duplicate the screw holes that fastened the masonite to the interior structure, But I used chromed countersunk, philips-head screws identical to the rest of the garnish mouldings in the interior, but these with panel washers. They did not use the same door panel clips in the '55 Courier for the rear masonite wall panels, only the screws. Furthermore, as I recall, there isn't that much surface material to the interior structure to have a 1/4" diameter hole for the door panel clips back there around the perimeter.