A100/A108 interior panels

Just curious what people are using for interior panels in their vans. My '69 A108 Travco Family Wagon camper I believe originally had fiberglass or plastic panels that covered the interior for a smoother look than seeing the body sheet metal and supports. All but one of mine are gone now. I am about to insulate the walls and floor of the van for heat and sound and don't want to see the insulation when I'm done. Are you using thin plywood, plastic, carpet, curtains? Just looking for ideas.

Thanks all.

try looking here.
https://vintage-vans.forumotion.com/f44-interiors