It's a good idea to abandon amp gauge. They are fire starters. Volt meter very easy to install.
As far as originalish. It's all about the diameter of gauge, color of face and sweep.
I do not know if you are wanting to put gauge in original position or a period looking hang down. Putting into the gauge cluster will be very hard. Probably about a 90 deg sweep gauge positioned so that needle sweeps old markings.
Got $850?
http://www.tuckersparts.com/Tach-Force-Gauge-Cluster-TF01B.html
For hang down: Auto Meter has several styles that will look good: "Old Tyme Black", "Traditional Chrome", etc. or a Ebay original SW working gauge. Who ever looks at an amp or volt meter? When battery goes dead you will know it. Then check alternator output and go from there. Carry a cell phone and credit card.


Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn