On cold start-up my 66 idles showing 14.5 volts or so. It runs and drives without fluctuation staying between 14-15 volts on the initial drive. I have verified this with a voltmeter and it matches the guage on the dash.

But I noticed after I drive the car and turn it off and then restart it after a stop at the store, the voltage always drops and reads near 12 volts at idle. When I give it gas and start driving the voltage goes back up over 14 but then drops back to near 12 at a stop light...

Voltage drop after driving