I just saw this post.I have fiberglas fenders ,too. The car had painted mounts and small lights on it when I got it,so I bought shortenedchrome mounts and big '34 lights from Vintique. I've been playing with them for over a year now and can't get them aimed right. The driverside points at the ground and the passenger side shoots way up. 

The old lights didn't do this.Maybe I'll try the old mounts on the new lights and see what happens.