Hi my fuel gauge is not working right on my 1982 chevy camaro it doesnt say how much gas it has it goes back and forth when stop and go's so what could it be?

 

If the gauge reflects the motion of the car, it sounds like the float sensor in the fuel tank needs attention.

 

my fuel tank has no sending unit, the old one was rusted and broke. could i install a aftermarket sending unit with a new fuel level guage. i know auto meter has a big selection. how do i decide which rating to use. i see 0 to 90 ohms,ect. does it matter which rating i use or does the fuel tank require a specfic ohm empty to full rating.