I have a 73 camaro ,and the gas gauge stays past full .The car has no gas in tank. Also my temp gauge goes to hot when I turn the switch off, Then drops down when I turn key on. The car runs, but this happens before the car has been started, so the motor cant be hot.I have replaced the circuit board behind the gauges but that did not help.It must be a short or Ground but I cant find it .If someone has had this problem please give me some advice.Thanks .
SteveW

 

Sounds like a missing ground from the gauge panel to the body. On the back of the gauges, there is usually a male spade terminal sticking out that a ground wire goes to. Look and see if it is still on. Probably pulled off when the gauges were removed, and is hanging down in the wire loom.

 

Is the gas float in the tank stuck? If not, make sure the sender's ground wire is in contact with some bare metal.