Brake light ground issue

If the sockets are protruding from the back of your tail light housing, solder on a ground wire, and ground it to the body. Just find an indiscreet place to screw it on. I had to do this on my 67, and 69 B-Cudas front turn sig/park lights.
Some times you have to replace the brass contacts in the base of the socket, also. I have actually soldered on more solder to them.
Dave