i did a tub out 57 chevy pickup built a steel fuel safe for a fuel cell built a frame out of 1by1 tubing to hold below the wood bed and built a batter box that slid on a rack with pins and was bolted so if you need to get at the batter you unbolted the bolt pull it 1 inch off the pins and it would come out all of it was painted a body color and all was above the roll pan the owner made up a filler neck up that was flush with the deck like a boat filler neck