After Market Ammeter?

As much as I used to like ammeters I finally caved and went voltmeter.

Start by reading this MAD article, which covers a lot of ground as to inherent problems in these old girls

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

This might give you some ideas if you decide to "do" a voltmeter.

http://www.forabodiesonly.com/mopar/showthread.php?t=119480