Your tail light bezels arn't making a good ground with the bulb sockets and/or the sockets are corroded.
As far as the lights surgeing..... that's due to the under powered alt, as the engine speeds up the alt produces more juice... so the lights get brighter, as you turn on more assy they will get dimmer etc....... best thing I ever did for mine was to convert the old external regulator to a modern internal regulated, more powerful, alt. It was as simple as unbolting the old alt, installing the new one, removing the external regulator, jumping the four wires from the old reg, replacing the pig tail on the alt and adding a new feed wire.
I used a painless re-wire kit and re-wired mine took two weekends, cured all my electrical gremlins. It was very straight fwd and easy to do.
Last edited by EOD Guy; 11-04-2012 at 03:13 AM.