Factory ammeter

Even Ma Mopar identified this problem back in the day. In fleet vehicles (cop cars and taxis) they bypassed the bulkhead connector with the two wires that go to the ammeter and ran them through a grommet in the firewall. you can do the same, or if you don't want it to look altered, gut your bulkhead connector where those two wires pass through and run the wires all the way through with a better connector under the dash. If you use a connector that you can pull through the bulkhead connector, you can still disconnect the wires under the dash and then disconnect the bulkhead connector and pull those wires out on the engine bay side when needed.

If you have access to an electrical rebuild shop, they can spin the alternator and measure the output. Factory Service manual (usually available on line) will tell you what the original alternators put out for standard, with AC and fleet vehicles. I'm a big fan of ammeters - I'd rather know if the system was overcharging or not charging before a voltmeter tells me it's too late - both a voltmeter and an ammeter is ideal.