I did this for years and never even thought twice about it....
The gas gauge didn't work but I could tell if I had an 1/8th of a tank or any level for that matter just by dropping the tail light, opening the gas cap, shaking the car, and then put my head near the filler neck. My friends and I never ran out of gas, but one time one of my friend's asked me if ever gave any thought as to how goofy it looked. Once I thought about it I had to laugh because it really never crossed my mind up until then.
I mean imagine a car full of teens in a primer grey '56 Chevy 210, blaring loud music and with loud exhaust catching attention besides the overall cool-factor of the car itself rumbling up into a parking stall at a gas station, not at the pumps, the driver getting out and walking to the drivers side rear of the car, turning a knob on the tail light and dropping it down, twisting off the gas cap, grabbing the back quarter panel and shaking the car violently and then listening to the tail light, then putting the cap back on, flipping up the tail light and getting back in the car and driving off.
My stepdad eventually figured out the wiring and got the gauge working, so no more goofy tail light listening...lol...