After cleaning and sealing a few tanks, I would rather buy a new tank at $140. I believe the repro tanks are most all made from a MFG in Canada and the quality is good for the two I've installed. I bought a $140 tank off eBay and it was the same tank as the much more expensive one I'd bought previously.
Of the tank sealers I researched, all had a warning about a chemical you cannot put in the tank after sealing. Most all octane boosters have one of the chemicals you are warned not to use. Of the types of tank sealers available, I've used the one that is not sensitive to MEK.