I know this is an old thread, but I just went through this on my '72 Camaro.
For 10 years I ran my stock wiring (external regulator) with what was given to me as a stock replacement alternator. Turns out it was a 63-amp 10SI model, which is internally regulated. Contrary to what you may have read elsewhere, there's really no problem running your external regulator on top of the internal one (except you have to change the plug to the alternator from parallel-blade to serial-blade, no big deal). However, lately the beast started acting oddly, and it smelled like an issue with the old electromechanical (read: relays involved) regulator.
Rather than replace it, I simply bypassed it as advised in various places. Terminals on the regulator are marked F 2 3 4. I just shorted the F wire to the 4 wire, and the 2 wire to the 3 wire. I used good old wire nuts. No diodes involved, since I still have my stock harness. Works like a charm, in fact better than before since the regulator's contact blades were, as it turns out, pretty rusty. If you don't have your stock wiring harness, it's possible (or so I read) that the motor won't want to shut off, and you need to install a diode between the 4 wire and the F wire. Make sure it's big enough to handle the current load. The arrow on the diode symbol should point toward the F wire. In other words, if you have a regular diode and it's black with a white stripe on one end, that white stripe should be on the side connected to the F wire.
If you have an old Camaro, be aware that I wound up with my internal-regulator 10SI because Advance Auto considers it a stock replacement for a '72 Camaro. Technically, it is not. For a '75, e.g., yes. But it will work fine on a stock '72 with a new plug for the alternator and the steps I mentioned above.
If you're bent on keeping the car 'original' (and you probably wouldn't be here if you were), you want a 10DN unregulated alternator that requires the external regulator.