I may just be in over my head here but I'm seriously considering ripping an old HUD off a GM car in a junkyard and hardwiring it into my Hyundai. I already plan to convert the interior lights red so the dash will be pulled apart anyway at some point. So my question is does the HUD in GM cars just rely on a signal from the car or does all of the computing take place elsewhere? I'm to worried about the complexity, I'm in school to become an electrical engineer, but I do want to assess the situation so any input would be awesome.

I don't know about the HUD in pre-2K Bonneville'* but you will not be able to wire one in from anything 2K+. Although there are a few discreet signals (signal lights and one or two others), the majority of data is acquired from the Class 2 Serial Data Bus. Your Hyundai will not support this.

Someone may be able to comment on '99 and earlier, but you're out of luck in the latter years

Oh I'm sure I would have put together some kind of converter board but looky what I found!!!
http://www.nippon-seiki.co.jp/defish...ncept_top.html

It looks ghetto but I'd have it flush mounted with my dashboard to look clean, loving the RPM readout on that thing, not cheap tho but about the same price as the radar detector I have.

Again, the GM HUD is quite specific. You need to remember that these units have a display capable of the following:

Cassette Symbol
High Beam Symbol
"AM" Flag
"FM" Flag
CD Number
Track Number
"CHECK GAGES" Flag
Fuel Pump Symbol
MPH Flag
KM/H Flag
Speed Information

The GM HUD (in the Bonneville) is not made up of pixels. Therefore, what'* above is what you get. It isn't configurable, the segments are "hard wired" as part of the fluorescent display. Several of these (particularly the entertainment items) are retrieved over the data bus, but are specific only to GM.

You may get portions to work, but I very much doubt that it will work as designed.

you would want a HUD from a 96-99. this will have the electronic adjustment

after that the HUD is only 8 wires...your PCM need to send out the 4000 pulses per minute for the speedo to work. everything else is straight forward....spend some time with FSM'*

Hmmm....I am thinking if you can find one, get a first generation from a Cuttlass Suprememe. They were surface mounted, rudimentary in design, and should be fairly easy to install.

I doubt very seriously you will be able to get the speedo to work though. It uses a 4k pulse signal that comes straight from the PCM, and IIRC, was proprietary to GM.