Alternator Pains

I have a voltage drop at the regulator of about .7 of a volt and from the reading i've been doing i think would make the alt increase the voltage roughly that amount.I'm not the person to throw parts at something i actually did a bit of testing.I traced the voltage drop to the inside plug on the fire wall that kind of leads me to believe it may be some resistance in the ignition switch.I also checked the wiring around the choke as its the same cir that goes to the alt and regulator. The choke has a heater witch may cause a voltage drop.By removing the choke wire with car running and engine cold watching a meter the voltage would change but only .1 So with the possibility of the ignition switch being the problem i thought a 1 wire alt might be solution to eliminate some of the 50 year old wiring and also solve the problem.It seems to have happened over time i have a volt gauge in the car and confirmed correct with my meter.It kind of puzzels me that I get 15 volts at high rpm wouldn't the regulator hold the voltage at a certain amount no matter how high the rpm.Thanks for the help and i didn't buy that one wire alt yet lol i'm open to any suggestions.