[Peter Serio]

One more thing you might consider; have you checked the printed circuit at the back of the gauge housing? Those go bad when they get old and they will peel apart. The "GEN" lamp flashing on & off is a sign that the current is seeking a path to ground of least resistance. There are a pair of turn signal tell tails in the dash which are routed thru the printed circuit also double check your ground straps behind the plastic dash bezel.

There are 2 places of copper "footprints" in the PC that have small 1/4" hex head screws overlapping the copper into the steel of the gauge housing. Those 2 screws transfer ground from your PC into the housing. The housing then transfers that over to the LH side lower ground strap and onto the painted tab of the interior dash lower cowl.

The point of contact to the car's body is the short one on the LH side right below the wiper switch. There is a threaded stud in the bezel that sandwiches that ground strap onto what is a painted part of the cowl which forms the lower part of the dash. You should sand off the paint on that one area so the ground strap has a nice clean patch of bright metal.