FYI
Square back and round back alternators are the same for hooking up (providing the alternators have the same two lead plugs) and both are externally regulated with the regulator on the firewall.
What you are seeing is the differences in the shape of the
installed diodes (alternators need diodes to convert the AC power from the electrical field to DC power
). Round back diodes are in cans Vs square back diodes are open to the air for better cooling.
Only the aftermarket single wire alternator (main power wire only) has a regulator internally and this is attached to the outside of alternator because there is no room on the inside.
Hope this help..