Here is part of a wiring diagram from my 47-54 GMC maintenance manual showing the neutral safety switch for the models with hydramatic transmissions. The switch is in the top left corner of the diagram inside the dotted lines.

http://community.webshots.com/photo/551791889/2106130080090990065oYsiQt


"Nothing astonishes men so much as common sense and plain dealing." - Ralph Waldo Emerson