Stop in for a cup of coffee

Where are you measureing voltage?
other possibility is the regulator is not breaking the ground - assuming its negative controlling VR.
Is it the brush or wire grounding?
If not then maybe bad regulator.
70’s regulator,2 pin. i trimmed the wiring out of a good harness,
Nothing is taped off or rubbing anywhere. Two regulators, same result. Block to body grounded, clean connections. Im baffled. only thing i can think of is the ground strap isnt heavy enough.
the only connections so far is coil and alternator. Not a single other connection in the entire truck.
Had to drive it out of shop, back in on friday afternoon.
I referred to this diagram, alt and reg wiring only.

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