67 Barracuda Fuel gauge problems

You dont really even need to jack the car up to test the gauge. Locate the sender wire inside the trunk. Its almost directly above the differential. Shove a shirt pin through the wire casing and jumper that pin to chassis ground. The trunk lid hasp is a good unpainted ground point. Now turn the switch on. If the gauge needle goes to maximum position, turn the switch off and remove the jumper. The problem is under the car. If the needle doesn't respond properly, send the gauge to me and I'll fix it.