I towed with a 2003 Expy 5.4L (2-valve version) 3.73 towing a 6000 Lb. trailer with wife and 2 kids. I did it but I would highly recommend you stay at or below a 5000 lb. trailer to provide a more comfortable ride. I got pushed around a lot by the trailer when towing even with a good anti-sway hitch. Couldn't tow in the mountains well at all. I would go for a newer Expy (with the 4-valve version and higher tow capacity) or better yet an Excursion V10. You may even look at the GMC/Suburban as they may have higher tow capacities.
