Gas gauge and grounding the sending unit
 

I have an 83 with a not working gas gauge while playing around I found out if I ground out the center bolt on the sending unit the fuel gauge works. This is an 83 with a 2 wire sending unit. Was there supposed to be a ground there? Can I just solder a ground on and be done?

there may have been a grounding strap between the tank and underside of the car.

No, thats a common problem with the sender. In mine I ran a wire from the center section to one of the mount bolts for fix the ground.

Also make sure you have the ground wire between the chassis and muffler in the rear.

I took a better look and the yellow wire terminal is tied to the center of the unit I tried removing yellow and just running ground to that terminal , no gauge. I added a ground tied into the yellow and voila gauge not really sure why it works but it does call it a win.