I recently stumbled across a pair of N.O.S. passenger side only inner door trim panels, GM part #3686116. I installed the better of the two in my ‘48 Chevy ½ ton 5-window deluxe truck. Pictured is the N.O.S. door panel paired with a N.O.S. arm rest.
Prior to the find, maroon Spanish grain vinyl material from Jim Carter was glued to a standard door panel. The photo compares the Carter material with the NOS door panel.