Stop light switch is a simple on-off switch. When brake is depressed the switch transfers the 12v on terminal from light switch to terminal going to lights. With an ohm meter between the switch terminal (no wires connected) it should go from infinite to 0 ohms as you move the lever open and closed. If you short the wires together you should get brake lights.

http://chevy.oldcarmanualproject.com/shop/1955truck2/55ctsm1202.htm



Ed