Right?
The Camaro spoiler is almost identical to Randy's except taller and with slightly more of a "V" shape (less straight). You should be able to mount it to your lower radiator support and bumper without any modifications to the car, it will go smoother if you have a heat gun to use on the spoiler but it's not mandatory.
As far as what else will help you, you're keeping us far too much in the dark for anyone to have a good idea of what to suggest. There are people here that take their cars on road courses at the kinds of speeds you're talking about, but unless you give us a better idea of how your car is set up and what you're actually planning on doing there isn't much anyone can say.
And what QA1 stuff do you have? Because right now a Stage II QA1 system is a full coilover conversion. Clearly you don't have that. But even a Stage I system has upper and lower tubular control arms with a tubular K, so I'm curious what you'll do to the "lower front end" that will help. Did you install all new suspension and leave the old wheel bearings?
You really aren't giving us much to work with. If you started by answering autoxcuda's questions from post #27 it would be a good start.