Sorry I didn't see this until now.
As David says I have factory AC in my 1969 410. (Also factory electric windows and door armrests.) The car is away being rewired at the moment but you can see a couple of overview pictures of the installation here:
https://www.classicandsportscar.com/...tionary-rebels
When the car is back (next month I hope) I can take some more detailed pictures and update the thread.
The hazard warning switch has not been moved from the usual location and can still be operated even if it can't be seen!
Rather than move the footwell vent lever, my car has separate levers for driver and passenger vents, one on each side.
Overall the AC works very well, and is especially good at refrigerating the driver's left knee. Ventilation to the rear seats is improved with the back widows open. It does however raise the engine temperature by as much as 10º or more when cruising, and if stuck in traffic the cooling system struggles to cope with the AC on top of its regular duties. I believe it is wired to run the fans constantly when the AC is on.