Battery Drain Question

[YourBuddy'sTruck]

Something was draining my battery down overnight.
With a little research here, I found how to test what it was at the fuse block.
One by one, nothing was pulling any current.
So then I tested Voltage OFF, Idle, and at 800RPM.
My battery is fine and the Alternator is charging while running.
So I then performed the test with the meter between the Negative Post and the Cable and it was showing a full 12V draw.
Next - Start unplugging things till you find it, right?
First thing I see in front of me is the pigtail on top of the Alternator and think that can't be it, but do it anyway to rule it out.
Low and behold, the draw went away!
So I left it unplugged overnight and sure enough the battery was not drained this morning.
This 3-Wire Alternator is Internally Regulated.
Is this the Voltage Regulator that is bad?
Can it be replaced or should I get a whole new Alternator.

It's a 350 with HEI and old Voltage Regulator Bypassed.
No other electrical or ignition modifications on this vehicle.
Thanks for you thoughts before I reach for a wrench.