[VetteVet]

Nice rig you have their Nikwho.
You should take your alternator to any Autozone and have them test it for you. If it's bad I would upgrade to a CS 144 because it cools better and it has a little more output.
You don't need a separate ground because the alternator grounds itself through it's mounting bracket. You can get one through Summit Racing or Jegs or just about any of the aftermarket suppliers.

Wiring it up is simple as DJLambert has explained. You just need the L and S wiring terminals and a resister ( 35 to 500 ohms) wired in series with the L wire.

You may have damaged the alternator when you wired the L terminal with a hot circuit wire. If it was key on hot then you may be OK but you would still need the resistor.
Your rebel harness should have a designated, key on, hot wire for the L terminal unless you got a stock harness from them. They should have sent a schematic or a wiring diagram with it.

Your 59 was wired stock with the power wires going straight through the Amp meter and GM deleted that setup in 1963 with the new style ammeter (battery gauge)and then in 1974 with the voltmeter. Your harness should be adapted to fit one of those, hopefully it is the voltmeter style.

Refer to the thread that DJ posted above and all your questions should be answered.