How to take out ammeter cluster?

Can anyone guide me on how to take this baby off?

I’m trying to get it converted to a volt meter by Rocketman.

Take the two nuts off the back.  They hold the ammeter on as well as make the connections to the circuit.  

However, I've ruined two gauges because the studs turned when I turned the nuts, and that broke an internal wire.  So instead of using a nutdriver I now use a wrench and hold the end of the stud with pliers the first time I take one off.