tb82, I did not read through all the posts, but can give you some food for thought on the aux gas tank in the bed. Sure you cannot doa a gravity feed. however on mine i installed a typical 12 in line fuel pump between the aux and the main filler neck. Draw the gas from the tube in the top of the tank that has the pick up from the bottom. Put a veton 12 vol normally closed valve between the outlet of the fuel pump and the inlet to the filler neck. Power those two puppies up to a switch like the upfitter in the Ford. So you can flip the switch and replenish the fuel in the main when you want to. Since the fuel valve closes the Ford fuel system is shut when not refueling, I did an open vent on the aux and down through the bed with and in line filter since i am paranoid about having an open vent to the tank..