i have never heard of the old behind the seat tanks exploding i saw a 66 burn up once after a roll over and the gas laeking from the tank ignited.how ever it is concievable that if the truck got rear ended hard enough it could crush the back of the cab and tank.i replaced the stock tank on a 66 GMC with one from a suburban for the extra cab space it was pretty much a bolt on deal.the hard part is deciding where to put the filler cap.
