a/c install

Its nearly impossible.   I say that because it can be done, with LOTS and LOTS of work.

You would need the entire heater box assembly from the donor car. You would need to gut the entire front compartment, and 3/4 of the interior.

You would have to get the Servos x2 for the new heater box, rewire your cabin harness to accept the new A/C puss button heater controls, you would need a new heater core for an A/C car.   And we have not even gotten the dryer, condenser and compressor lines that need to go all the way under the car. Plus you you would need an A/C Compressor bracket at the back of the car, and also wire in the A/C harness into the engine harness, if your old car did not have A/C you'll have to find an Oil Pressure Switch extension tube to relocate the Oil Pressure Sender.

        I am probably only have done with the explanation, it is nearly impossible to swap. I would say 10x harder than even doing an Auto to Stick swap. Which I have done in the past.

If you want A/C find a donor Fiero with A/C and build around that car.