Re: Air con?
I believe so. I'm not sure about the Twinspark but the 30 litre 12 valve cars can be done from under the bonnet. It's no small undertaking though. You'll obviously need a pump on the engine & associated bracketry plus the wires for it. The condenser will go in front of the radiator and will need the hoses running round the engine bay to and from it. The evaporator & receiver / dryer can (I'm told) go into the heater box from the engine side but the false bulkhead needs to come out and maybe the top few bits of engine to get at it. Finally, some sort of control unit inside the car - don't know if the wires will be behind the dash for the climate control type heater control unit if the "manual" one was fitted originally. Of course, you could just have a simple on-off switch for the aircon compressor instead.
You'd need the bits off the latest cars with R134a as the refrigerant. The older cars use R12 and that's no longer available. The hoses & seals for each are incompatible.