Thanks for the reply Dave
When I got home from work, I did a voltage drop test across the body ground cable, the 8ga. wire between the Rt. side head and the Rt. fender apron, engine running or off, 0.00 volts. Checked voltage drop across both positive and negative battery cables, less than .5v on both while cranking. Checked voltage drop from case of regulator to the body, 0.0v. Disconnected and checked voltage of yellow/black wire from the GEN light circuit at the regulator, had 11.7 volts with key on. Started engine, revved to 2,000 rpm, had 15.8 volts at ARM terminal of regulator, 4.8v at the FLD terminal, 11.7v at BAT terminal. Cutout relay never closed, GEN light obviously still on. I even checked to make sure the bulb was correct, it was (57). I have to be missing something, but this keeps telling me there's something amiss with the regulator. But its currently (no pun intended) on its 3rd one, so I have a hard time believing that's the issue. Possible, but not probable. I find it odd that Ford put that small external ground wire from the generator to the regulator mounting tab, seems redundant but I'm sure the engineers had a good reason for putting it there. 0v drop from the generator ground lug to the regulator base. Just for grins I checked the resistance of the field windings with the field wire disconnected, showed 6.5 ohms. The armature is a new old stock piece from Mac's.
I normally love a good electrical challenge but this one is kicking me arse! All the other circuits in the car work fine. What should I look at next?
Thanks for the help, greatly appreciated! Tim