[patrickt]

Originally Posted by cycleguy55

While ammeters are traditional and probably more 'period correct', voltmeters are the way to go, IMO. Apparently I'm not alone: Ammeter vs. Voltmeter: Which is Better? - Hot Rod Network

Ammeters get an undeserved bum's treatment from the internet car sites. Except for when the battery is recharging right after you fire her up, a properly laid out wiring harness has very little amperage going through the ammeter when you're driving it. Plus, better ammeters don't run the entire wire full of current through the gauge itself, only a portion of it is shunted through it. If you know your car really well, then either a volt meter or an amp meter is going to tip you off if something is amiss. So it's really just a matter of personal preference.