well the HID option isn't just a simple swap of a bulb and your done..
the the OEM Celica HID... it actually uses a specially designed Headlamp made specifically for HID so you also get the nice purpleness.. and the size that stock hid system's use is D2R/D2S ..
compared to stock halogen low beams which uses h7 (on the celica)
heres some differences between the stock and hid headlamp since i have both.. https://www.celicahobby.com/ubbthrea...&PHPSESSID=
in my opinion if you have the money and want to do things right.. just get the OEM HID headlamps then you're pretty much set..
theres more to it but thats about it