If it is not too far gone there is always POR 15:
Fuel System repair This product is for the inside the tank - you can use the regular product on the outside. It takes practice to work with if you are worried about aesthetics. If you get it to thick it will wrinkle when it dries - no big deal for stuff underneath a driver . . .
The trick is timing the top coat. Top coat too early more wrinkles . . . You must top coat before it cures cause once it cures nothing thins it or sticks to to it . . .
regards,
stock49