This right here might be a clue. Often the regulator is not at fault but if it's a mechanical type it could be. But VOLTAGE DROP in the harness or ground WILL cause overvoltage, and bad connections in the harness will. This is a VERY common problem. Try disconnecting the IGN terminal of the VR, and connecting a temporary jumper from there direct to the batter and see if things "settle down," both the flicker and the over--voltage. With battery "up and normal" and the engine warm, and running at high idle, measure battery voltage. Should run about 13.5--14.2V
MAKE CERTAIN, absolutely certain, that the VR is grounded, and that the battery has a good ground path to the body
I like to add a BIG ground jumper. Look at the holes in the end of the pass. side head. Those same holes are unused on the firewall end of the driver's head. Add a short "starter" cable (eyelet to eyelet) about a foot long from a short bolt into the head, to the firewall. The mounting studs for the master cylinder are good.
