No prob. If its a stock AWD system, its a BW4405.

The 4406 came in the F150 in the manual shift version, and in the Expedition with the electric shift. Theres a bunch of guys that have dropped the 4405, and installed the 4406. This writeup gives you the parts list and pretty clear directions.
http://www.explorerforum.com/forums/showthread.php?t=166726&page=2
If you search theres a bunch of guys that have done it, so in theory you could possibly have it under there.
Good luck with your sale, and hope you and yours had a great christmas