I added an ATI(Aluminum Tank Indistries) 51 gallon tank to the bed of my truck a while back. I love having the extra fuel as I don't have to stop at JUST truck stops. This gives me a total of 88 gallons of fuel when both are full. It is a gravity fed system and only took about 45 minutes to install. However, I wired in a 12V valve from Valves4projects on Ebay to my upfitter switch so I can choose when I want to add fuel or IF I want to add fuel. Since I already had a toolbox, I wasn't concerned with a bed cover but I did want as much bed space as possible, so my tank is only 9" wide. This is a pic of my setup.
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