How much modification are you planning to do on the truck, keep stock or build up more off road capabilities? Reason I ask is I want to mod my truck some so adding an extra tank is in the plan. I want larger tires which could mean the spare might not fit under the bed. So I want to build a rear swing out rack to carry a spare behind the tailgate. This frees up the space under the bed which is the place where the gas tank for the full size two door SUV's was located. Chevy Blaer or ford bronco both had rear tanks and some long bed trucks had a second tank there so my eventual plan is to buy a tank intended for replacement in one of those and mount it there.