WARNING: This page is about a different car, the 2004 Ford RV Cutaway, 2004 Ford Econoline, 2004 Ford E450 Super Duty, and 2004 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Assembly Plant
Courtesy of FORD MOTOR CO.
The eleventh VIN position is the assembly plant code.