The AC unit for a period correct look would be like attached.
This has the evaporator, fan and controls for the system. Requires two lines from the engine compartment to this unit.
This unit bolts to the bottom of the instrument panel.
This specific unit is on Ebay for $550, which seems rather high. But everything is high right now.
In the upper left you can see the cut lines
At least one electrical connector is seen as well.
Blower fan is in the back
Provisions for condensate drain would need to be made too so that would be additional hole(s)
Action