For Dana's '56 3100 I used a Panel/Suburban tank that mounts between the passenger side frame rail and the driveshaft. I really didn't want to use a in-bed filler as we knew we were going to add a tonneau cover to secure our luggage when we travel and we didn't want the luggage to smell like gas if it dripped while filling. The Suburban tank also allowed us to retain the spare tire in it's factory location, a must for long distance travel. A bonus is that this tank is a direct bolt is as the frames are all made the same. The only down side is the tank is only 15 gallons.
For the filler door I used Tanks Inc Filler Door FFD-A and cut it into the rear passenger fender just behind the tire. It basically took (2) fuel rated 90* rubber hoses and a straight piece of thin wall galvanized pipe to plumb it out. The only tricky thing was getting the vent done, I connected copper tubing to the factory tank vent and ran it inside the fender well to the underside of the top of the fender then bent a U-turn and dropped it down to the bottom of the fender so if it puked any gas it would just drip on the ground and not on the fender or frame.
https://www.tanksinc.com/index.cfm/...=466/category_id=-1/mode=prod/prd466.htmMike B
