Judging by the fact that they say it will be held at the "California Speedway drag strip in Fontana" I am assuming it is a dragrace?
Knowing what the track looks like is crucial to your design. The straightness of the track is a very important factor in determining the shape of your car. A dragster will not fair well in a slalom.
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J&H Hobbies near my house was a long time record holder for the worlds fastest RC car.
The car they raced was a suped up model dragster.
They used electric motors, because they had better acceleration. The frame was made from carbon-fiber for rigidity. And it featured two super big wheels in the back for extra pushing traction.
Here's another modified racer I found online.
http://www.rccaraction.com/rc/articles/need_speed.asp
Realize however that these cars would fit easily into the size limits (40"), wasting a lot of space. Your best bet is in using bigger motors and more batteries.
Checking out the RobotMarketPlace is a good idea.