Replacing Ignition Switch in 73 Duster

The end of the switch lever can only fit into the lock cylinder one way, so I doubt that's your problem.

Is there any chance someone has monkey'd with the wiring downstream of the switch connector? I'd inspect the harness from the switch connector to the starter relay and look for homemade splices.

I'd also want to make sure someone hadn't moved wires from one connector cavity to another for some bizarre reason. You'd need a wiring diagram with color codes to verify that.

http://70duster440.com/DashHarness70 Page 2 and 3.PDF