I've looked into it, and was going to take it on, but some parts i'd lined up fell thru.
You need quite a few bits.
Compressor and bracket, this can come from any 4cyl, and should jsut bolt on.
Aircon pipes and radiator
The actual heaterbox itself is different, so you'll need a complete AC heater box, along with the climate unit, centre console and wiring harness.
Theres also likely the odd bit of extra wiring here and there that you'll have to make up, or patch in, for example the stuff for the electric fans.
You'd have to be pretty attached to the car, or have a particularly good example, to make it worth your while. Isnt the ADR a naturally asthmatic 1.8? Unless its particularly tidy, your probably better off shifting it on and buying a car with it ready fitted, and a turbo engine.