Please read carefully what is being posted here. Regardless of "round back" or "square back" a round back can have ONE or TWO field connections. The two is known as ISOLATED FIELD and was used starting in '70 but!!!........
There are TWO regulators. The "up through 69" regulator hooks to switched ignition power and the field wire and you ground it. Done That is used with a single terminal field alternator. If you have TWO simply ground the remaining field
The flat looking electronic used in 70/ later wires exactly the same EXCEPT the alternator must have two field connections, and the last field terminal is wired to switched ignition power.
So the "flat" 70/ later gets ground, ignition power, wire to one field, and second field goes to switched power
The early 69/ earlier regulator gets ground, ignition power, and wire to the only field connection
Simple