I'm pretty sure that by 1966 they had gone to a resistor wire from the ignition switch to the coil. It's a fabric-insulated nickel/chrome wire that drops the voltage to about 9.5 volts with the engine running. To test primary voltage at the coil, be sure the points are closed, turn the ignition switch to the "run" position, and check the voltage at the coil (+) terminal. It should be about 9 volts. Voltage at the coil (-) terminal with the points closed and the switch on should be almost zero. With the points open, the reading will go up to the same voltage as the battery at both coil terminals. There should be a bypass wire from the I terminal at the starter solenoid to the coil + terminal. During cranking, this applies full battery voltage to the coil and bypasses the resistance wire. Be sure you've got clean, properly-adjusted points. The most common cause of a no-start condition is dirty or burned points, or insufficient point gap.
Jerry
