I wanted a little more time between fill ups mainly for convenience on long trips. I picked up a 5th wheel style aluminum tank off craigslist and went to work. I cut the bottom out of the tool box to add a the 55 gallon aluminum fuel tank. I used a fuel tank selector switch kit made for the 1997 and previous Ford Pre-Super Dutys (it is a tank selector kit including valve with return line ports, switch, and wire harness with instructions) so I can now select between the two tanks (stock fuel gauge shows level for tank that is being used). This gives me a new highway running distance of about 1500 miles or 1100 mile city between fill ups unloaded...
Inside the tool box
Classy selector valve shield I made to protect it from road debris.
Selector switch that came with the kit, doesn't really match the dash, but works and is factory labeled main and aux.
on all the powerstrokes the pump is frame mounted and is basicly insiide the frame under the drives door.
as long as you are using the oem pump you should be good this will keep the ineratia swich still as a safty devise.
Yes, I am using the stock fuel pump. I spliced into the stock fuel lines on top of the factory tank (they are a lot smaller than I expected). I was under the impression that as long as I stayed under 110 gal in the bed of the truck, it would be DOT compliant. Either way, since it is hidden, I'm not worried about being pulled over for it.
It gravity feeds to the stock filler neck (the aux tank just keeps the main tank topped off until empty). Been in the truck for over a year without issue. No extra pumps, no wiring and no switches to install in your truck.