The above link gives you the tow ratings for a 2005 EXT. Max trailer wts vary from 4800# to 5700#, depending on your engine and tranny. However read the notes carefully. They are based on a base vehicle (no options) with one person on board. And they caution you on tongue weight vs the rear axle rating. So figure out what your vehicle really weighs as ready for travel and go from there. Hope this helps a little.
2001 Ford F-250 PSD, Line-X, 3 ISSPRO gauges, TTM, Cyclone Fan, pulling a MobileScout 30RKS (loaded), Maxxair, Honda EU 2000. USAF retired.