I have a problem with my '69 Barracuda I believe to be a grounding issue, but do not know where to look. My brake lights and turn signals work fine while operating without the headlights on. When I turn the headlights on the left brake light goes out completly when applying the brakes and that same turn signal operates very slowly while the headlights are on.

Left taillight socket-ground problem most likely.

Thanks. What would be the best/easiest way to ground it? I am not real familiar with electrical repairs. I have some eyelets, some wire and some other wiring repair stuff.

Just try removing the bulb and be sure it's clean in the socket and the bulbs metal base.Try a new bulb. Tighten up the tail light housing which is how it grounds.

Make sure the bulb isnt in backwards also.Easy to get them in wrong.Rocky