big volts

In and out of the bulkhead,Yes.
-With the engine off,key run,the headlights and heater off,and the blue wires off: (the alt, the VR, and the B-resistor), Battery voltage should be everywhere about the same. That would be; the A1-10Red circuit that goes from the battery to the ammeter, the R6-12Blk circuit that goes from the ammeter to the alt output stud, and every open circuit blue wire if/when the ig sw is in run.And every blue wire should drop to zero with key off.
-With engine off,key in run;As each disconnected item is reconnected expect the voltage to drop a bit, until you get to the alt. Here disconnect the green wire from it first. the when you reconnect the blue to the alt, there should be very little change in the voltmeter.Then if you ground the terminal where the green wire came off(full fielding it), the voltage should drop quite a bit, as the armature sucks up electrons from the battery. Then as the battery recovers the voltage might pop back up a bit.Do not leave the green wire grounded longer than necessary to complete the test. A few seconds is all you need.
-So thats the yes answer.

Now, if you again disconnect the VR and the alt field wires, and then start the car; the voltage should again be everywhere about the same as measured on the supply side of the devices, and be battery voltage.Then when you connect the VR to the blue(green off the alt), expect a small drop in voltage, and with the green still off the alt, no change when the blue is reconnected to the alt.At this point the engine is running 100% on battery power.If you were to turn on the lights or/and heater at this time, the voltage would drop everywhere to a new level but nearly the same throughout the system(the alt is not yet on line).
-Ok so, lights and heater off, lets reconnect the green wire to the alt.Now, if the VR is good and has a good ground, it should immediately pump the voltage up to its set point, which could be in the neighborhood of 13 to 14 or more volts.It does this by grounding the green wire.As the senses the voltage rise at the blue wire, it shuts off the alt, which causes the voltage an the blue wire to fall, which the VR again sees, and turns the alt back on. It does all this seesawing so fast that the analog meters never catch it.They will just read the average voltage. It will be seesawing between battery rest voltage and its set-point. It could be between 10 or 11 volts on a really flat battery and the set-point, or as the battery comes up, it could be switching from 12 or 13 volts to its set-point.If you have a digital VOM it probably wont catch it either.

-Now as to the large voltage spikes.I dont understand them either.The full field numbers are good, with a 1 volt drop from alt to batt. That same or similar drop should show up on the blue wire, anywhere along its length on the supply side of any device.
-The only thing I can figure is that the alt is pumping out an A/C spike and your meter is catching it, cause remember;during full-fielding, the VR is out of circuit. If that were true, then the alt is bad, having at least one perforated diode. But that alt was tested and passed. So I just dont know. I have a box full of used alternators here. I would be trying a different one, and retesting.
-Well, a thought just occurred to me. If there was an intermittent short, or a regularly pulsing high-current draw, anywhere in the electrics, the VR could be responding to it, by rapidly turning the alt on/off, full-bore. There is only one device that fits that description; the ig coil. I would think the stock coil would be too feeble to do that, and the B-resistor should damp it out.Youre not running an MSD are you?In either case these devices could only evoke a spike while the engine is running.
IDK Barbee. This is as tough as it gets.

PS; since your not calling out circuit codes,colors or wire sizes, Ima guessing you havent yet extracted these circuits from the wiring diagram. I think it would be really advantageous to you if you did. If I had a way of posting it for you I would. I tried to create something with the keyboard, but it turned into crap when I previewed it.