If your existing tank is in decent shape, you can get it cleaned / repaired as per above suggestions. If you want to relocate it under the bed, you can purchase steel or poly tanks that locate to the rear of the axle for around $ 200. Some guys have also used tanks from assorted junk yard vehicles. Fillers can be located in the bed, or routed out the sides. Have a look at Chevs of the '40's, or Summit Racing Equipment for ideas.
