Originally Posted by pfogle

Get some masonite and some R-13 or R-16 fiberglass house insulation. Stuff the insulation in every nook and cranny you can, then use the masonite (or luan, or 1/4 inch finish grade ply) to cover it. It'll look nice and be a lot better insulated. We've done that to two of them. One was an '83 E350 15 pass that needed some help, and the other was an '04 E150 cargo, it helps a lot with road noise and the hvac system.