I replaced the alternator in my 71 Mark III and still can't get it to work (replaced the external voltage reg too). I'm thinking I might not have a wire on the right terminal on the back of the alternator. There is a harness with 2 wires. One being the battery and one being the switched power? I have the battery terminal screwed on to the BAT (red terminal on the back of the alternator) and the snap on connecter to the white terminal next to it that is labled FLD. Then there is a stray wire that was connected somewhere and I don't remember where. The issue is that the stray wire wasn't connected to anything on the other end. It has a female plug on the other end which led up to the carburetor area but I don't know where it connected to originally. Does this connect to either the GRD or STA terminal? I only had 3 wires connected to the alternator when I took the original one out? Looks like there should be more? I don't know what any previous owners might have bypassed or disconnected etc.

I attached of an alternator for reference. Thanks for any help!

 

This goes back a ways, but if I recall there was a wire from the S stator terminal that went to the automatic choke heater coil. Will do a little more checking and hopefully can help solve your concerns.
Have to go back and check if the system had a "A" or "B" set up for the charging system. One supplied voltage to the alt field and the other supplied a ground to the field. Whichever system it has you can full field the alt to bypass the voltage regulator and confirm whether the problem is either the alt or voltage regulator. Will try to get back with the correct system used.

 

It is important to know how you are determining that the charging system is not charging. If you are going by the AMP gauge on the dash, forget it, and connect a test voltmeter to the battery and read the actual voltage at the battery. There were concerns regarding the amp meter readings on some of those vintage Fords.

 

I got it to work. The wires were shot in the harness. I just rewired it and all is good. Thanks for the help!