Auxillary Fuel Tank
I have a 60 gallon tank/tool box combo purchased from Northern Tool. It is T'd into the filler hose of the OEM tank and uses a small electric fuel pump to transfer the fuel. When the truck fuel gage gets low I just turn the dash mounted switch on (w/ red indicator light) and let it run until the tank is full, then turn it off. It's wired into a circuit that is only hot when the key is on. I also installed a return line back to the tank in the OEM filler hose to prevent overfilling. Total cost was less than $700 and I now carry 86 gallons.
2014 Jayco Jay Flight 33RLDS travel trailer, 2005 Chevy 2500 Duramax diesel with 60 gallon auxilary bed mounted fuel tank, Honda EU3000 generator.