To be honest it depends on how much 'grief' you want doing it )
I'm pretty sure the non-A/C cars have the power steering pump in a different location, so that and all the pipework would need to be moved first.
Then fitting the A/C system itself.. condenser needs to be fitted behind the dash along with the heater matrix/core and the black cover that covers that up below the windscreen would need to be replaced.
But I think you would need to swap/replace the engine bay loom as that would contain the wiring for the A/C.
You may even need to swap/replace the loom inside the car.
None of it would necessarily be hard, but a fair bit of work I would say.
It may be easier to get a universal kit intended for custom builds and hot rods. They have everything in one box so you dont have to try to make the existing wiring work, you just add new extra wiring.