I have a Powermaster 105 amp single wire alternator in my 69, I was taking voltage and amp readings after I moved the battery to the trunk and noticed the stock voltage regulator was connected . My question is do I need this connected? or should I simply un-plug it. What is the downside to leaving it connected, or is it even doing anything because I understand the single wire alternator is internally regulated, right?

Yes, that single wire alternator is internally regulated!....Merely unplug the original external voltage regulator and/or remove it!

You might take the disconnected VR plug and jumper the two inside terminals together and jumper the the two outside terminals together. This way the GEN light should work as normal.

What is the impact of not disconnecting the external VR? Would that cause problems for the new internally regulated alternator?

GEN light would not go out because the excite wire is not connected from the ign switch IF the int reg alt is 3-wire configured.

If new alt is wired as a 1-wire, GEN light will not go out.

Thanks Everett. I had the external VR plugged in, while running an internally regulated alternator, and had been experiencing a loss of power when the headlights were turned on. I unplugged the external VR. Issue resolved. Does that indicate that the two voltage regulators were "fighting" each other?

Yes, it does. Does the GEN work, meaning comes with IGN on and goes off with alternator working?

My car has the center console guage pod. The under dash wiring harness I ordered did not come with a plug for the GEN light in the dash, so I don't have that issue.

Cool!