With a Mach you can't just just swap the dash out from 71 to 73... nah that would be too convenient. The engineers were bored and designed different harnesses w/different connectors for laughs. You have to have the same column to go with it.
Several months later, I'm going back through the electrical problems on my stang. I noticed the Turn signal switch in the column, is the one w/ the different connection from 71-73.