Squareback vs round back alternator?

CLBER said

If I understand right the additional relay reduces ballast in J2 wiring to the dash and guides the biggest charing load in the eng compartment wiring, right

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All the relay does is feeds the voltage regulator with 100% battery voltage. Otherwise you could have a voltage drop at every connection and switch along the path from the battery to the voltage regulator, giving the voltage regulator a false battery reading causing it to tell the alternator to charge at a higher voltage.

(After this is all done I would love to know how different the older European cars are as compared to our A bodies. )