I thought what Metaldoc did here was super cool. If I ever switch to an under bed tank this is what I'll do.
http://67-72chevytrucks.com/vboard/s...45#post7586745
If I keep my in-cab tank and add an under bed tank, then I'm going to use valves and pumps to move fuel to and from the in-cab tank and just not have a filler neck at all on my under bed tank.