So I cracked my drivers side headlight, and I was looking into replacing both of them already anyways. In my searches I noticed some of the aftermarket ones say they aren't compatible with the stock HID. Why aren't they compatible? Is it just a bulb thing, or is there something completely different with the headlights? To everyone that's going to say get the 06+ headlights, I'm already considering them, but keeping my views broad at the moment.

03 Touring in case anyone needs that.

 

The bulb openings are different i believe the base headlights use a h1 bulbs while the HID use a D2R bulb also they have a opening at the bottom to mount the ballast.

This are the ones u need
http://www.ebay.com/itm/03-05-Nissan-350Z-HID-Xenon-Headlights-Headlamps-Left-Right-Lamp-Pair-Set-NEW-/130933327536?pt=Motors_Car_Truck_Parts_Accessories&fits=Model%3A350Z&hash=item1e7c3c06b0&vxp=mtr

 

If I was going to go with a pair that doesn't "fit" the HID models, what would I have to do to get them to fit and work properly?

 

^run an aftermarket hid setup (usually not of oem quality) or modify it to fit your oem setup. however if you get an aftermarket light setup with a projector, the oem 03-05 setups bulb will not work as it is a reflective type, per the oem housing. the 06+ bulb type is required for a true projector.

in truth your best bet is to buy oem 03-05 spec, or 06+ oem spec.