The 2-terminal alternator has what's called an "isolated field" system. There is no internal ground for the alternator field coil. It you choose to use the 2-terminal alternator, just ground one of the field terminals (doesn't matter which one) and run the original field wire from your existing regulator to the remaining field terminal.

The factory wiring for the isolated field alternator ran 12 volts to one field terminal, and put the regulator on the ground side. That one takes a different regulator so the simplest way is to create an external ground for the replacement alternator.
Jerry

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