Alternator wiring question

Yes sir.
Thanks for the tip. Had not considered looking for a difference in potential at those points.
I like it when I don't have to think about things.

Going a off topic, just because you are watching.
My "driver" is giving me fits. 318 cop engine, Q-jet. All "stock" stuff.
This is the car that I think I sent someone a flaky orange box to do a post mortem on. That box was causing a rough idle but good at RPMs above idle.

The car has just developed a "mis" at low RPM under load. Not rough, but a "mis". Like it's shutting off for a micro second.
Does it under under load and acceration to a point. Then clear.
I opened and checked the carb.
I even swapped on spare Q jet today and have looked for VAC leaks. VAC is steady. 20 at free idle. 15 in gear.
So I'm thinking somthing in the igniton. But a timing light flashes good and I've looked at the wires in the dark to find arcing. Nothing seems off.
The mis gets worse as the car is driven. Hotter. Maybe the ballast (single) resistor.
I'll post when I find out.
Tomorrow when I have all day, I'll start swapping parts, change wires and get new plugs
(I've found Autolite AP 66 run best in my 318 setups. The ones in this car may be 7 years old or better.)