Yes, it can be done. Not quite straight forward though. The HIDs have different plugs and different numbers of bulbs. Also, I ran a relayed setup. I got Lightwerkz in the USA to custom make me a plug-and-play adaptor harness, it made everything a lot easier. Even then, Jason had to swap some of the connectors to make it all mate up properly. We couldn\'t figure out where the factory ballast mounts went, so we just discarded them and drilled mounting holes for the ballasts directly under the HID housings. Worked fine.
Be aware that the Spec C doesn\'t have the sensors and wiring for the levelling motors, so there will be an unfilled plug at the back of the housings once the conversion is done. Dunno if that makes the HIDs illegal in NZ, but they are illegal in Europe without the levelling function.
The HIDs got sold off when I parted out bits of the car prior to sale. Figured I\'d get more for them separately than selling them with the car. Also, they\'re a lot heavier than the factory ones, so you will violate the lightweight spirit of your Spec C if you go HIDs!
You can retrofit HID bulbs into non-HID housings, but because HID outputs a completely different pattern of light distribution from the bulb, the reflectors will not work and you will get a lot of blinding scatter rather than a tight focused beam. You may actually end up seeing less, despite the extra brightness! This is why I went with factory HIDs.