I think I would investigate your reading of..."the alternator positive post to positive battery post differential, ~.7 V." I see the sine wave symbol. What is that all about? You have to use the DC setting of voltage.
That .7V is way to high. You want it to be just like the negative cable. Even .2 is on the high side. Under .1 is better on big cables!
A tiny Voltage difference means a exponentially high resistance.
The big positive cable is in two pieces on the way to the alternator by the way of the starter motor.
So that's three corrosion or loose points.
I also like Art's bad brushes or worn slip ring idea for low slow speed output. The exciter current is fed through the positive side fuse of the cars cluster he talks about.
You could say we are both on the positive side of this issue! (:-)
Phil
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