If my car ever makes it to a track I will probably use a screen from Intensity, it will at least keep rocks and birds out. I can only fit a 10x2.75 air cleaner on my car and there's no way it will feed a 500" engine at WOT. Speaker covers work also, as Sixpackgut mentioned.

I had a 340 Scamp years ago that ran great with a 14x5 K&N but my big block cars have always slowed down with an air cleaner so I ran for many years without one.

http://intensityracingproducts.com/proseriesscreens.html