Alternator Vs Generator

Like all early CJs my M38A1 originally had a generator and regulator. At an unknown rate mine was switched out for an alternator with an internal regulator.

I'm rewiring the Jeep. My military maintenance manual tells me there is a wire running from the gen/reg output B terminal to the positive ammeter terminal and a wire from the gen/reg output D terminal to the negative ammeter terminal.

Eliminating the generator and regulator has simplified these circuits. A wire from the alternator to the starter. Hot power comes off of the starter to the various circuits.

I've forgotten more than I've ever known so trying to remember how the voltmeter was wired before I pulled it is impossible so I need help. Here is a pic of the gauge. The only thing I'm sure of is there was a small ground wire running from the ground terminal to one of the brackets holding the gauge in place. From left to right the terminals are marked "G" "S" and "I".

Unless I'm wrong G is the ground. Is the S terminal where the wire for the starter goes, and I to the ignition switch?

For whatever reason, the S terminal is quite a bit shorter. There's just a little more room to add a ringed connector before you reach the point the nut won't be fully seated.

 

Correction I have a wire coming off of the alternator from the same terminal that links the alternator and starter. I'm not sure yet what it's purpose is but it's fairly long.

 

It's a voltmeter. Not an amateur.

Any insight into the G, S and I terminals?