As long as your power source doesn't cut out when you engage the starter you are fine. You know how everything quits when you turn the key all the way to start? The 69 has the ignition switch on the lower column and provides power to the coil during this period of cranking. If the 68 has this built into the dash switch then you are good to go. I looked at the 68 wiring diagram and compared it to the 69 wiring diagram to come up with the idea that they were different. No guessing.
