hi there, I don't know if you got this problem figured out already... but I had the same problem in my '71. The turn signal lever/high beam switch had broken and it wouldn't stay in the on position. Also my Hi/Low relay was bad. I changed the relay...then I removed the instrument cluster so that I could access the wires entering the dash from the turn signal lever. I wiring diagram will tell you what colors the hi/lo will be. Not wanting to pay for a whole new lever, I installed a simple switch on the dash to turn on the highs. Again, I don't know if any of this helps, and if you need to know more about how to test or rewire it just let me know.