Fluttering Voltage, Backfire, Engine Quits

Hello. Running original wiring in restored 69 Cuda. Have the usual issues as with any other Mopar I've owned ie: dim lights, slow signal lights with headlights on, voltage shows low at idle, etc, etc.
But.....the other day out for a cruise and all of a sudden my voltage gauge tach's hard to the left (low), back to center and keeps fluttering while the car tries to die, then backfires, than goes again driving fine but with the voltage gauge still fluttering like crazy. The repeats with backfiring, engine trying to die, then volt gauge back to centre and drives normal till I get home. Once home and hood open I could hear my alternator (only a year old) rattling like a bearing was going or something.
I have never had this happen before. I have had an alternator give out in the past, but just wouldn't charge the system. Never a total kill of the engine and the voltage tach'ing erratically low like that. I just recently put a new voltage regulator, but maybe that's crapping out?
Are alternators known to do that at times? Is this what they call a "Dead Short"? Electrical is Voodoo to me, so I'm in the dark.
Any help would be very much appreciated.