Ammeter to Voltmeter...who does it?

You want switched 12, but you also want to make darn sure that you have fixed the voltage drop problems in the harness/ connectors/ switches etc. "Ignition run" originally feeds the regulator sense line, so that is what you want. "Accessory" would work if you don't mind, or maybe even want the meter powered with the key in that position. I used the same switched power that feeds the cluster/ gauges. Just tap in where power comes into the gauges voltage limiter.