I don’t know what year tank you’re looking at but the one I have for my 1956 Clipper looks good, although I‘ve not yet installed it. Others have done so and are happy with it. The same tank is proper back to 1952 but also fits 1951 if you don’t care that he fill whistle is gone.
For sealer, I‘ve always used Hirsch gas tank sealer with excellent results. A tank I coated with it back in the ‘70s or early ‘80s still had the smell and color of proper gasoline when I drained it a few years ago even though it was too old to burn properly.