Overcharging Please Help

Hey everyone, I have a 71 duster with a 3 wire alt two field and one B+. and electronic reg. When I start the car it is sitting at 16v and when I rev it up it goes to 18 volts and the headlights start to flash. The alt is new and I also took one of my suberbee and tried that with no luck. The reg has been replaced twice because I thought that was the problem the entire time. I checked for volts on the field circuit and I am getting 12.5 volts (KOEO) to the blue wire on the alt. I disconnected the green wire that goes from the alt to the reg and checked continuity to ground (assuming I had a shord to ground) and I have no continuity, I have also ran a new green wire just to be sure from the alt to the reg and no luck. Please help me, have anyone seen this before? I dont think I have any bad grounds but that is where I am going to look next. Can bad grounds cause overcharging? I would think it would cause it not to charge. I have a big cruis night tomorrow and I want to get it fixed tonight.