Good luck understanding a wire diagram- its good for connecting wires, but if you want to understand it you need a schematic. This is for a 69 , but all the classics are very similar. Do you have an automatic? It sounds like you aren't getting power to terminal S of the starter solenoid. It could be the neutral safety switch (even an adjustment) if you have an automatic, or no power from Ignition switch S. Before you randomly replace parts, get an inexpensive volt-ohm meter and check for 12v at those places I just mentioned. Its cheaper than replacing parts. One lead goes to the chassis (or battery negative), and the other to those places. On the schematic, power generally runs from left (the battery + terminal) to right. Read those notes. If you need help holler.
