I still have the original gas tank on my '57 T-Bird. No holes or serious problems that I am aware of but the guy who restored my dual quad carbs recommended that I replace the tank or clean and seal it. Thinking about having a radiator shop boil it out and use the new gas tank sealer. Hate to spend the money for  new tank if I don't have to but do not want to have a problem later that would be worse.