fuel tanks

me and a friend of mine are almost done putting a 54 chevy p/u on a 1991 s-10 frame. we were going to use the cab mounted factory tank from the 54 but it is leaking so we need to use something else. we can buy an aftermarket cell from summit, but we would rather use something cheaper, and better suited for our situation. i have been told that there are some s-10 blazers or astrovans that have tanks that are mounted in the rear of the truck as opposed to the side mounted tank out of the s-10 pickup. if anyone can help me with the years of the blazer i am looking for please reply. or if you have other ideas, let me know. and we also have an old beer keg we have been toying with using.