Ah Ha....pics are worth a thousand... whatever...
That IS NOT a one wire GM alternator, but a 10-SI alternator. a one wire will have a plastic plug there, but same chassis.
On the two pronged plug in, it needs an 'exciter' wire run from battery voltage. GM does this by going from the large post to the '2' terminal.
The other terminal (1) goes to a 'hot' with the key on. this may need a resistor in this wire to prevent 'back feeding' the system, so when the key is off the engine doesn't keep running.
Hope this helps.
Dan'l