Amy Winehouse

1969 VW Beetle Charging System Problem?

My 1969 VW Baja Bug is having some problems with the charging system. According to the voltmeter in the car at idle, it is just under 12 volts, and with the headlights on, it goes down to 10ish volts. If a wire is disconnected from the ignition coil (with power power on but not running obviously) , the voltmeter in the car goes to 12. I hooked my multimeter up to the battery to confirm and it gave me a different reading. At idle, it is putting out about 12.3 volts and with the headlights on, it puts out about 12 volts. If I rev up, the voltage does not go up like it should. I have replaced the generator, voltage regulator, negative battery cable, and some wires going to the voltage regulator. The tension on the belt is good. If I shut the car off, the voltage from the battery goes up to 12.4. Any ideas on the cause of this problem would be appreciated. http://www.cardomain.com/ride/2958381
It has an external voltage regulator. Also, the generator was polarized when installed.
Alternator kit is on the way!