One option on the headliner and door panels is a guy operating as White Wolf Speed Shop on Facebook, who makes ABS plastic headliner, half door panel, full door panel, and kick panel kits. The material won't disintegrate like the cardboard will. It comes in black, but I assume it can be painted with an appropriate type paint, or covered with a thin material. I have not dealt with him, but have seen plenty of interaction and positive feedback on the Facebook AD truck groups. I plan to buy a headliner and stock-size door panels in the future.
