I have the wiring diagram book for those year trucks and ya got me curious enough about the brakelight wire that I'm goin to dig the book out first thing tomorrow. I believe that the brakelight is powered at the fuseblock and then goes to the T/S switch, but I could be wrong. As for the wires on the starter solenoid, the purple is the start wire. The wire on the other small post goes to the positive post on the coil to bypass the ballast resistor while crankin the engine. Any wires on the large post with the battery cable are simply power supply wires for various systems and accesories.