Rallye Gauge A/C ?'s

That is going to be a challenge.Everything about the heat and air changed between 72 and 73. If someone hasn't already worked the puzzle before you, you will need to take a pre 73 factory service manuals info and a 73 up manual info and mesh them.
In the end you would be an expert on those vacuum manifolds.
It might be easier to just cut the later controller into the rallye panel.
Those mechanical push buttons were trouble makers anyway.
I'm subscribed here, interested in how it works out. Good luck