My 68 has a problem with the the amp meter jumping and at the same time the dash lights go dim and get brighter and am also having a problem with the headlights going dim at idle.They will brighten as rpm's go up.Any thoughts and or suggestions on what might be causing this and how to fix the problems.
Pretty typical. You can do a relay upgrade, do a search for headlight relay on this site, or you can upgrade the alternator. Denso 120 amp is going in mine. The latter will fix all the idle issues, I bet you can't really use the windshield wiper at idle either.
upgrade alternator and wires, beside a HARD mantenience job on bulkhead conectors and back of ammeter are the only solutions