Originally Posted by KLC
You could buy an auxiliary tank that mounts in the bed. To make it easy you could gravity feed it to your main tank with a ball valve.
^thats the most common thing i've seen.
You want to keep the gas tank centered in the truck, Saftey thing. If however, your ok with, (or you just don't have) a spare tire. thats plenty of room for another 5-10 gallon tank, depending on what you like. You'd just need a second Fuel pump, or lines to run it into the main system, then a switch to turn it all on.