JB Weld doesn't hold up to Dethanol fuel, ask me how I know..
Suggest cleaning out the inside of the tank with old gravel, then after it's clean and dry, use a quart of this stuff..
https://www.damonq.com/products/red-kote it's not cheap, but your tank will never leak again. After applying this stuff, you could slap some JB Weld on the outside if you still think it needs shoring up, as the internal coating will keep fuel from ever touching the JB Weld epoxy.
These days however, a new tank is just cheap insurance. You could even buy a new tank that relocates the flammable liquid storage outside the actual passenger compartment.
The last new tank I bought, I coated with red-kote before there was ever fuel in it. That way no one will ever have a problem with that tank, even if the fuel inside goes rotten, it won't rust the metal.
