another way to do it is buy a vintage air unit they fit under the dash where the old heater bit is out of sight and just keep the old heater cover under the bonnet so it still looks factory and then its all new . they have outlets so you just use ducting and run it up to your factory vents i am doing one in my HQ coupe so i will put up some photos when i can .as for cost the unit is about $800 and a brand new compressor is about $500 and there are other bits you will need but you should get away with it for under $2000 i know it sounds a lot but it will be all brand new and you wont have that big ugly factory unit under the bonnet . i know VK V8 commodores had their air cond compressor on the right side but not sure it will fit a HZ i bought a bracket off a HJ(not factory) and it has the compressor under the alternator and looks neat hope this helps