Gauge Wiring Help

[truckster]

I'm putting an EZ Wiring harness in my 72 Blazer, and while I'm at it I want to convert the ammeter to a voltmeter and convert the oil pressure from mechanical to electrical.

I have both gauges out of an 84 Chevy truck. I also have a new oil pressure sending unit for the same truck. I need to know which terminals to connect on the gauges.

The wiring harness has a wire marked "voltage gauge", so I believe one side of the gauge is grounded and the other is connected to the corresponding wire.

I believe the oil pressure gauge is grounded through the oil pressure sending unit, so one side should be +12v and the other connected to the oil pressure wire.

If anyone knows which terminal is which, I would really appreciate the help. Also, each gauge has a third terminal. Is that a ground, and does it need to be connected?

Thanks in advance.