Another Charging Question

There is no way to know if the alternator is bad from what you posted there. ALL alternators will "drop off" "at some point"

Are those voltages with the VR bypassed, in other words "full field" voltage to the field?

No, field hookup does not matter. You can reverse the wires.

Some possibilities...........

Alternator might not be "the one" you think it is. There is a difference in output with different alternators. As old as these girls are, and with the "mixup" in parts from rebuilders, that might be difficult to determine.

Alternator might just plain be turning over too slow. There is NO GUARANTEE that these girls every "put out" 14V at a dead idle, orginally!!!

Alternator might have a problem. Only "ways" to know that is to read the shop manual and perform a full load test, take it to a parts store with a "good tester" (which may or may not be) or to a rebuilder (local) who really knows what he is doing.

Here's a better question......."Does it really matter" that the voltage sags at a dead idle?