i stuck a peice of 3/8" plywood into the bed of my f150 in june 94. when i sold it a few months ago the bed looked like new underneath except it had lost its clearcoat. rest of the truck was rotted to death but the inside of the bed looked great. unless your hauling chunks of busted concrete or scrap metal or a lot of gravel or something like that, the sides don't take much of a beating. my used dodge i bought came with one of them slide-in jobs but if it hadn't i'd just done the plywood route.
