Here is what I do to my gas tanks: pull the tank out, remove the sender and drain plug after soaking it in acetone or reclaimed bodyshop thinner. This dissolves any gummed up gas. You can return the thinner to the bodyshop and they can re-claim it again. Sandblast it inside and out through all holes. If you find pinholes or leaks, I slightly indent them and then using a old bronze soldering hand iron, solder up the leaks. I then DA sand the solder like body filler. Then duct tape up the sender, filler, and install drain plug. Air up the tank to 2 lbs and spray soapy water on the repaired areas and seams to check for leaks. If all is good, paint it and you are good to go. I'm not impressed by tank creamers or sealers. Nothing sticks to rust for very long. A new CJ tank is really not too expensive, It's the military ones that are high. John