Mine did the same thing. Was connector from steering column to harness. Would wiggle when I worked the clutch. Zip tied it up secure and haven’t had a issue since
This 67 doesn't have ignition switch or main power wiring in column.
That connector on the fusible link is a known problem also. Pull it apart and find terminals corroded and/or melted away. Some are melted and wont pull apart without destroying the plastic.
