Guys, I think I have posted this before, but I use Caswell epoxy tank sealer. Once again, it is NOT cheap, but it is one of the absolute best ones on the market. It is a true epoxy, and after appropriate curing (depends upon temp), it is 100% impervious to any of the common fuels out there today, including pure ethanol, diesel, gasoline, kerosene, and high octane racing fuel. There is no better if you truly want to seal the inside of your fuel tank.
Once applied, you you won't dissolve it, nor will it flake off, soften, crack, or fail. I don't own stock in the company, but when I coat a tank, it is the only thing I use. Eastwood sells it. Ebay has it. Amazon has it. Caswell also sells direct.
So, if you want to do it once and never again, use it.http://www.caswellplating.com/restoration-aids/epoxy-gas-tank-sealer.html