[Mook]

I have the same issue, who ever had my GTO before me was too lazy to find the ground issues. So they soldered ground wires to each socket in the trunk and both parking lights in the front. I am in the process of removing them and tracking down an grounding issues. The first one I found is with the passenger side front parking/turn-signal socket for the bulb is bad. One of the springs sticks down. Thought I fixed it sat but while driving to day the blinker stopped working. I kept the blinker on it glowed then the fuse blew.

I say start looking for bad grounds, old sockets, wiring, wrong bulbs ......good luck