Problems replacing ignition switch on 75 D100

If red is the battery wire, it should have continuity to "something" in all positions except off and lock.

Seems like you are on the right track with continuity.

You should be able to probe the connector when installed, and test for "start" voltage. You sure you did not screw up the shift linkage, moving the column, etc? (Automatic? Clutch switch?)

What exactly does / does not work at this time?