I can see adding a volt meter, but don't get why people replace an ammeter with a volt meter. To me, the ammeter is the quickest way to spot a problem with the charging system, or for visualizing which systems, when turned on, are causing a current draw that the charging system can't satisfy...
40 year old wires, loose and cooroded connections, added electrical demand from today's modern electronic ignitions, electric fuel pumps, electric fans, GPS devices plugged into power outlets, aftermarket stereo systems with amps, etc and upgraded alternators putting out double the original amperage....
That's why
Lots of cars have suffered electrical fires from under the dash. Even a bone stock car, if you drained the battery and jump it, is now pushing 65 amps through a tiny 10 ga wire that passes through the firewall twice.
Bone stock restored car with old points ignition, and fresh clean wire harnesses and good connectors and the stock alternator, then you can go ahead and keep your amp gauge.