My gas gauge is always reading above Full. Thinking bad ground or broken ground. Where is the ground wire terminated at? In trunk,bumper, or frame.

 

The ground wire comes off the top of the sending unit and is connected to the chassis somewhere up under the car forward of the fuel tank. You're going to have to get down under the car to look for it. It's probably worth putting the rear up on jack stands so you have more room to get your arms up in there.

This figure is from page 8-14 of your '72 Olds chassis service manual. Note "view C."

 

The fuel level (float) sensor is the ground side of gauge circuit. Generally you have lost ground to the float, or its bad.

 

A break in the wire between the gauge and sending unit will have the same symptom. On my car, the signal wire was loose at the sending unit, and the ground wire was fine.