Ammeter to Voltmeter...who does it?

Does anyone have a pic of the mods to the backside of the cluster? I am needing to put some sort of gauge in.....
Scroll back to my earlier post. There are no mods required to the housing. The gauge drops right in the factory holes.
I put that red paper label from the Sunpro gauge on there rather than throw it away but it's not concealing anything.