From Post response here.
I was tired of dealing with the wimpy 26-gallon factory fuel tank and had to do something. Stopping every 190-220 miles for fuel was ridiculous, the bladder still could go another 100 miles.
I did not want to spend a lot of money on a toolbox/fuel tank combo or a full factory replacement so I went Ebay shopping. I found a 17 gallon fuel cell tank that fits under my toolbox, solenoid, tee and switch.
I can get an additional 14 gallons of fuel at a push of the button. Now I can worry less about where the next fuel station is located.
I added a bulkhead fitting to fuel cell for gravity fill.
I used a 2″ to 1/2″ reducer tee to tee into the fuel filler hose. I added hose clamps later because I bought the wrong size when installing.
I fused tapped an ignition fuse to power solenoid only when ignition is on. I wired the switch to light up when power is sent to the solenoid. I mounted the fuel switch next to my exhaust brake switch.
I wait for factory fuel tank to reach 1/4 level and push button to drain Aux tank into truck tank.