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.