75 doesn't start with key

This is a strange one for me.  I had previously pulled the dash to repair the odometer and tach, but when I got it back together, it would not turn over.  I pulled the steering column and adjusted the ignition switch (where the rod goes from the key switch to the actual ignition switch) and it then started fine.

But. . .

I had to pull the dash again to zero the tach, and the same problem -- no start.

Today I pulled the column again, checked the switch and it works fine.

I checked each segment of the wiring from the ignition switch to the starter, and found no continuity from the clutch switch (this is a manual trans.) to the starter motor.  I know some '75s had a seatbelt lockout override switch, and my wiring diagram shows this as the only thing between the clutch switch and the starter, but I don't see this on my car.

Any ideas on where a break may be?  Is there another relay somewhere?  Why does this seem to be related to pulling the driver's side dash?

I've wired a push button from the battery directly to the starter, so I do have a way to start it, but I'd like to get the key switch to work.

I had a 75' with intermittent start problems. So I replaced the switch on top of the column. And it fixed the problem. I then took apart the old switch and noticed the copper rollers in the switch has a little burn mark - so if the burn mark aligned no start!