If you got the power, many cars simply need a change in final drive ratios; usually 0.250-0.400 lower (numerically). I can't really say much more about gearing 'cuz it's all been said before elsewhere.
Also, downforce and ground clearance are not needed on this track; set both to minimum. That'll lower your drag and (slightly) reduce your frontal area, allowing you to knife through the air better.