Current (no pun intended) consensus on 1965 ammeters/wiring

The last issue which affects charging voltages---assuming the regulator/ alternator are OK and that the regulator is at the right setpoint...........is the actual voltage which the VR SEES AKA "voltage drop". This is a common issue

To check this, Turn the ignition to "run" with engine stopped. Stab one probe of your meter into the top of the battery POS post, and connect the remaining one to the VR IGN terminal. You are hoping for a very low reading, the lower the better. More than about .3V (3/10 of one volt) you need to look into it

Also check the ground circuit. To do that get the engine running on "fast idle" and do this check with all accessories off, and again with all of them on, headlights, radio, heater, whatever

Stab one probe into the top of the battery NEG post, an the other into the VR mounting flange. Again, the lower voltage reading the better, and zero is perfect