I don't think a back up is really needed, just check to make sure the first is in good shape - not corroded
Here's a basic question about the tank grounding. Where is the intended ground path.
The tank is mounted to the body with the "tar paper pad" - no direct ground there.
The tank is held in with the metal straps and j-bolts - maybe that's the direct path to chassis.
The fill tube fits into a rubber grommet - no ground there.
The ground strap jumps across the rubber connecting hose on the fuel line, but then the fuel line runs under the car, and is clipped in place underneath, with lots of opportunity for corrosion and poor electrical contact to develop over a short time. Furthermore, it snakes up to the engine bay, where there is a fuel filter attached with two rubber hoses, so there's no ground path there.
I ask because I have the blinking low fuel light, and as I drive over wash board bumps, there appears to be a vibration induced fluctuation of that light on and off. I did paint my tank and straps with clear krylon. Now I'm thinking that might not have been the best idea.
Inquiring minds want to know.....