Hey if your air box is cracked then you are really in luck because the K&N FIPK actually replaces the entire air box and the duct that takes in the air from the front of the truck.

They make a pretty good difference in power (I am loving mine more and more every day) and make an absolute awesome sound on wide open throttle!

Here is a page with some info on it. The picture on bottom of the page is actually a F-150 w/302 it jsut doesn't say it. Thats exactly how it looks when installed
http://www.knfilters.com/injectkt.htm

 

You'll want to look for a 1994 and newer box. The older types like ours pre-94 use a screwin top where the newer ones have a snap in.