Lately I have seen quite a few people running into problems with the mechanical brake light switches. When I had this problem with my 51, the PO had butchered the floor when installing the V-8 engine, moving the brake pedal to miss the exhaust manifold. I found it a lot easier to install a hydraulic brake light switch. The switch was readily available at NAPA. Just cut the line out of the master cylinder and put a tee fitting in to accommodate the hydraulic switch and run the wires to it.
A special thanks to Don Short for this article.