I'll add my experience. I had a '66 tank with bad rust. I bought Muriatic acid at Lowes and followed the directions on the Eastwood Gas tank repair kit I had purchased. I had to acid wash the tank more than they said, but I was happy with the rust removal. The white sealer was more than enough, so you might start by using only 3/4 of the bottle. Overall, I was pleased with the results. I hear that POR-15 makes a nice kit too.

One thing to keep in mind is that neither kit contains the Muriatic Acid, even though the POR-15 kit says it's complete. I imagine it has an acid wash, but I say get the gallon of Muriatic at Lowes and then you will have everything you need.

http://www.eastwood.com/ew-gas-tank-sealer-kits-for-cars.html

http://www.por15.com/FUEL-TANK-REPAIR-KIT/productinfo/FTRK/

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