From what I have seen when the Capitol City Fiero's ran on the Michigan International Speedway, the notchies pop some where over 120 and the GT fastbacks seem to go about 130. But, it varies for every car depending on how strong the springs are and all kinds of things. The last year I went there was a GT fastback behind me that popped about 130 while I was up to 150 without popping, I am assuming because I had hood vents. There is a lot of air pressure that builds up under the front hood which causes the lights to pop up. Once one goes the other one goes right after, because with one up it grabs more air and pushes that air rignt into the area behind the radiator.
You might really think about taping the lights to try and prevent this from happening. I would hate to see you pop a headlight and then rip it off or break it in some other way.
Do they allow people to watch the runs? I might want to go just to see how it goes. Then maybe next year I will think about doing it too.