According to the Haynes repair manual, 96-04 Mustang 4.6L engines all use a large O ring seal and 4 bolts to hold it to the engine and 4 bolts holding the pulley onto the shaft.
If it sticks once the bolts are removed, it says to take a plastic softblow hammer or place a piece of wood against it and tap the wood with a hammer until it loosens. :bigthumbsup