one wire Alternator and voltage regulator question
No idea what your instruction sheet says or looks like.
Only this, which indicates this model is an isolated field alternator.
http://www.powermastermotorsports.com/094__Chrysler_Alternators.pdf
Powermaster 75191 Powermaster Retro Alternators | Summit Racing
If this is what you have then you need to set up as shown in the thread about identifying chrysler alternators. There's a post there about using an isolated field alternator in place of a grounded field alternator.
Either of those regulators in your car will work - assuming they are not damaged.
The photos show the 75191 is a revised squareback. If thats what you have, those regulators may have trouble handling the field current.
battery off voltage of 12.54 V is a bit low. I'd put it on a charger.
I mentioned an ammeter earlier referencing an aftermarket gauge in the dash.
Still don't understand this.
Aftermarket or factory, an automotive ammeter shows current flowing in or out of the battery. Current is measured in amperes.
A voltmeter shows energy level between two locations. As a dash gage or underdash gage, one is ground and the other is someplace on the run or accessory circuits.