I just went through the same problem. Most voltage regulators you buy these days are junk and don't regulate voltage correctly. The first thing I would do is make sure your battery tests good. Test your alternator or have it tested at an Auto Part store. When you install the voltage regulator, make sure you have good ground, start the engine and let it run for a min, then rev it to ~2000rpm for a couple of minutes, that will set the regulator. Check your voltage when the car is at about 1200 RPM, should be around 13.5 -14.5 volts.
I hear a lot of folks praising the upgraded regulators that are electronic. You can pick one up for $20. I would try all this first before you change over to a single wire set-up.
