A couple of things.

Does that have an electronic regulator and 2 field wire alternator?

The reason I ask is my Dad had a 75 Gran Fury that refused to charge after changing everything out. He converted it back to a mechanical reg and single field connection alternator and it was fine. (those new fangled electronic regulators are junk with assorted profanities throughout )

A few years later he had the dash apart because the ammeter never really worked that well on it and he decided it was time to find out why. It turns out the connections were all green on it. He cleaned them up and low and behold the ammeter actually showed charge.

That got him thinking about the electronic regulator so he hooked that stuff back up and it worked fine.

He has a background in electronics and figured that the regulator sees a fully charged battery as resistance and shuts down the alternator. The problem is it saw the resistance from the bad ammeter connection and did the same thing.

Sorry for the rambling.

The other thing is if it has the older style ammeter and it goes open, it won't charge. On those all voltage from the alternator goes thru the bulkhead, thru the ammeter and then back thru the bulkhead to the battery. I forget what year they went to a shunt but I don't think they can cause the same problem except for what I described above unless it completely melts down and that usually results in a dash fire. Might be worth checking tho as you did short out the main alternator wire.

Make sure the regulator if it is electronic with a 2 field wire alternator, is well grounded as that is how it controls the field voltage (varies the ground). No ground, no charge.

Kevin