I just spoke to Titan Fuel Tanks yesterday because we're going to be driving through Idaho Falls this summer and I'm considering taking the 2 hours to have them replace the 37 gallon tank in my Longhorn TV. Total price for the 57 gallon tank, with shield, installation, taxes and filled to capacity is about $1,700. This includes a military/veteran's discount. To go with a Trax 3 bed mounted system is almost the same price but you wind up with 87 gallons vs. 57 gallons. The downside of the bed mounted (trax 3) tank is the loss of space there. The up side is a lot more fuel onboard. Pros and cons...
BTW, you can get Titan tanks at Amazon. Titan doesn't like that but... well, there ya go.