http://www.varsityfordparts.com/catalog.htm
This is the only ford parts catalog I could find with an illustration. It has to be the worst parts illustration I have ever seen. But if you look at the cover that goes over the element, part number 6, with a little cutting and shaping the Apexi filter will fit right in there. I don't know if this link will bring you directly to the illustration but just enter into the year a 2004 Ford Expedition and go under engine and then into air intake. This took me right to the horrible illustration but you can get the idea.