70 Duster ignition issue

Ok, my 70 Duster was running fine. Had her out for a drive with no issues. I returned her to the garage and the next day she wouldn't run, started right up but as soon as you let go of the key it dies. If you hold the key in the on position it will continue to run until you let go of the key. First I changed the ballast resitor and had the same issue. Next I changed the starter relay and same issue. So, I pulled the steering wheel, took apart the column and changed the ignition switch. When that did not solve my issue, I changed the key and tumbler. I have no idea what to try next, please help!