This has been the wierdest week! I have had 3 cars here develop charging problems. The Dart Sport was discharging. That turned out to be the Alt. field wires being flopped with one having frayed to less than half its thickness. The Frankenduster had a problem at the bulkhead. Now its the Camper 9000.
This has been a great truck for hauling. It came to me "pre-scratched" so I dont have to worry about scuffing the paint when hauling rock, trash, metal to recycle or whatever. I swapped in a 440 last summer. It simply needed more torque than the worn out 360 could give. The alternator went bad after the swap, so I changed it out. The guage hasn't worked the whole time I have had the truck, so the only clues were slow cranking. Now it started doing it again. I tried another alternator, then several voltage regulators I had from my stash. Each time I tested their worth by starting the engine, then pulling the negative battery cable. EACH time the motor stalled and died. I have a fat 2 guage ground strap from the block to the frame rail as well as the one that goes from the neg cable to the core support. One regulator allowed the motor to run about 3 seconds after pulling the batt cable off, but it still died. Using a cheapie Harbor Freight tester, the NEW battery showed 12.60 volts at idle and the Alternator showed exactly the same! I repeated the test with the headlights on and got the same result. The instructions in the box with the regulator stated that " You should never remove the battery cables while the engine is running due to possible damage to the charging system. I have never heard of this, any opinions?
I suspected the guage was causing some sort of resistance, so I pulled the cluster and tied the guage leads together. NO CHANGE. I had the Alternator tested. It was good. I bought a new regulator and put it on. I retested the voltage and they still match! I compared the voltage on another car and as I suspected, the output at the Alternator was higher than at the battery. My next plan is to put in another battery with a lower state of charge and see if the Alternator output drops to the same number.... Any suggestions on what to do?
Finally... What is the ideal? My Duster test subject showed 13.50 at the alternator at a fast idle. Alt had the small 2 1/2" pulley. The battery was at 12.61.

you need to bring the RPM up to see if it's charging , mopar system sometimes will not show the 14 volts at idle .

I usually do give a quick rev. I remember hearing that some aftermarket alternators require a rise in RPM to 1500 or so for the ALT to take a set and begin charging. This setup is all stock. I have a few running Mopars here to test. All seem to charge even at idle.
I have a nice looking chrome POWERMASTER alternator that worked for about 14 minutes, then crapped out. It sucks because I really like how it looks! I had it rebuilt and it failed again later. W H Y ???

Voltage lower at the battery than at the alternator is due to resistance in the wiring. Since you've disabled the gauge, there's no reason to have it run in and out of the bulkhead. You can run a wire straight from the alternator output to the battery. Some will say it should be fused.

(1) need switched 12V to the alt field lead w the blue wire and (2) to the (flat 70's & up) VR terminal that has the blue wire on it. (3) good connection between the alt field terminal w the green wire and the other VR terminal w the green wire. That is correct that a batt should not be disconnected from an running engine. Your alt tested (at the shop) good, I'm assuming a good VR, that only leaves the supporting wiring. when you solve it if you choose to keep the ammeter disabled, connect the batt (or starter relay) to the alt w an 8 gauge cable protected w a 12 ga fusible link (NAPA has them I believe)

Thanks guys. I replaced the Voltage regulator with a $22 BWD unit. The wiring IS 36 years old, but what isnt wrapped in black tape actually looks good. Is it safe to believe that as long as the voltage is even or higher at the Alternator, than all is well?

The voltage should be the same (at least in theory). There's going to be some resistance, but like I said, there's no reason now why you need to take your charging current in through the bulkhead and back out to the battery.

U P D A T E :
The old truck did fine on a 23 mile round trip to the local dump. ZERO starting problems. I haven't tested ALT output with the handheld tester again, but the starter still spins fast.
NOW the Frankenduster has a wierd problem.... SUPER high output at the alternator. The battery tests at 13.10 at idle and the ALt shows 15.31 ! Too much? seems like it to me. The guage reads about 30 volts positive. What the heck, man???

30 volts or 30 amps?
If the batt is only getting 13.1, the alt is putting out 15 to try to charge the battery. Resistance in the charging wire is the culprit.