ALT gauge issues- clicks and pulses 69 DART. NEED HELP!!!

1969 Dart GT with 1976 360
Holley 670 Avenger
8mm Super stock wires
Champion RN12YC plugs
MSD Blaster 2 coil
Pertronics Ignitor/Electronic ignition
New battery, alternator and regulator (approx 3mo ago)

Noticed last week that it was sluggish in 1st gear... and backfired once thru carb. Thought it wasnt getting adequate gas (as you could goose the gas pedal to get it going) but definitely something wrong, but seemed to smooth out once you got going (and noted a broken plug wire).

So now the Alt needle/gauge clicks and pulses every 10 sec or so (see video). NOTE: Engine does NOT fluctuate as gauge pulses... maintains stable idle.

I just changed plugs, plug wires (one was broken at distrib) and distrib cap and had alternator tested (ok).

I know I will need a new harness and know the bulkhead connection is not in great shape... but hoping there is something else that may be culprit (could it be the gauge in the cluster?). I pulled cluster and did not see anything burned/fried.

Cant download videos? Heres a link with car off/key on: https://cvws.icloud-content.com/B/A...5D97&p=21&s=UrhXjVSW6dQ1Onk_f1dSlVvp7uI&teh=1

Any ideas? Thanks for any/all help.