Classic/Antique Car Repair: gas guge 79 0olds cutlass supreme, cutlass supreme, gas gauge

Question
my gas gauge works rarely and seems to work only when  I run out of gas completely and then fill it up I want to fix it my self because i cant find any shops who work on such old cars with that specific problem, how do I fix it myself?

Answer
Sounds like a float problem.

Your would have to drop the tank (best done when empty !). It is fairly simple, old cars usually have to straps holding tank.

Then pull the float assembly and either get one from a junk yard (relatively close model car, but does not need be exact) or buy an aftermarket gizmo from someone like JC Whitney.