Amp Meter Jumping & Head Lights Flickering.

Check all the wires in the bulkhead connector, especially the hot wire coming from the main battery terminal on the alternator (the one that connects to the stud on the back of the alt)...

I would also suggest looking under the dash. I had a "flickering gauge and light problem" in a 69 Valiant, and it turned out that some of the wires under the dash overheated, melted the insulation off, then would make intermittant short as the car vibrated down the road against the dash frame... I was going through alternators and regulators in 6-9 months.. Trace the main power wire under the dash that comes from the alternator mentioned above into the dash, up through the gauge, then to the fuse block...

After rewiring all the bad wires under the dash and the main charging and ignition system under the hood, I never blew another alternator or regulator for the rest of the life of the car....