still having problems, need advice please

Sorry for the late response, the hurricane was causing erratic power fluctuations here at the house. So, I turned off the computer for a day or so.

12.3 volts, engine running as you know is bad.
14.0 volts +/- .2 volts is target value for alternator output.

Engine off, ignition key in Run position:
One field lead to the alternator should be battery voltage. (12.3 or even about 11.5 is o.k.)
Just probe the back of the slip on connector.
We'll call that F1.
Do you have battery voltage at that connector?
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The other field lead goes back to the regulator.
Call it F2.
Disconnect that wire. Leave it disconnected.
With your ohm meter, measures ohms on that wire.
(it goes back to the regulator)
Should be a low ohm reading. .5 or so.
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If you have battery voltage going to F1 and a ground or nearly so on the F2 wire going back to the regulator. Then the alternator is the problem or it's case ground.
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Connect you multi meter to the battery posts to monitor battery voltage.
Start the engine. Idle rpm, only.
Clip a jumper on the alternator field terminal(F2) you just disconnected the wire from. For a brief moment, ground the other end of that jumper wire to the block. Just touch it.
You should get maximum alternator output and probably 15 volts at your meter. (sensitive equipment like stereoes, if "on" could get fried.
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If that checks o.k., then you have a bad voltage regulator. (or the wires going to and from it).