I've seen two hud conversions with regular glass. The difference in image isn't enough that most would notice, however..yes there is a special window for HUD.

Now back to the cost of a 2000 Hud window for our Potatoland buddy.

I sure noticed the double image when mine was accidentally replaced with standard glass - really prominent at night. The guy that does my windshields uses only top-quality glass, so maybe it'* a little thicker than the cheap stuff. That would separate the second image slightly, making it more noticable. When he replaced it with HUD glass, the projected image was sharp and crisp. I was happy.

The HUD will reflect off the inner surface and outer surface of the glass. All windshields have a layer of plastic sandwiched in the middle (safety glass). HUD windshields use that plastic to refract the image so when it hits the outer surface it doesn't interfere with the reflection off the inner surface. That'* what I was told anyway.

I wish I could tell you what my HUD glass cost, but I let my insurance take care of that. I think it was in the $700 range for my 93. If you're selling the car, find the cheapest HUD glass locally and have it replaced. Hmmm. Since it sounds like you're paying out of your own pocket, maybe you want to do that even if you're going to keep the car. I kept full coverage on my Bonnie and I'm glad I did, had mine changed with good quality glass by the best guy in town.

I had mine changed last summer at Safelite Auto Glass. It ran me around $450 bucks installed. Hope this helps you out.

Don't you have like two dozen of them in your parts warehouse?