Alternator gauge very erratic.

If you haven't addressed the bulkhead connector issues (search MAD Bypass), it is amazing your bulkhead hasn't already melted in corrosive WI, so jump on that (1963 & 65 owners don't have that issue). The VR needs a good connection to BAT- to work correctly. A rusty factory sheet-metal screw into the body may not get that done after 49 years.