...3 Recommendations:
1. Replace Alternator with 100 amp alternator, with INTERNAL Voltage regulator, and INTERNAL Cooling FAN. 'Hall Pantera' use to have these. The Internal Regulator Totally Eliminates the 'External Regulator'! I Big Leap for Panterakind!!
2. Install a Battery Disconnect switch of ground wire in front Bonnet.
3. Use a 12 Volt Battery TENDER, at ALL times when the Pantera is Not Running. Especially when Sitting Over Night! This was My Biggest Help, in Our HOT Valley, and My Garage! Really Keeps the Battery ALIVE!
ALL of Your Problems will Disappear...and Every Morning and Stop, Your Cleveland will Fire Right UP First Time, Everytime!!
You have My Personal Guarantee!
MJ
...P.S. The 'Voltmeter' was Your Best Idea! I'am sure you have noticed, after a Start, Your Charging 14+ Volts, slowly creeps down to 13.6 Volts, Running, Shown on My LED Digital Gauge. 12.2 Volts Not Running, ALL Electricals ON.