If you compare 2 identical trucks, say a 2500 4X4 auto, and a HO 6 spd, the difference in towing is substantial. Now if you mildly bomb the rig, say DD II's, Deluxe Blue Chip Wizard Fuel Mgmt Box. mild turbo upgrade from Piers, and of course a modified transmission - wouldn't this setup be more than what a 6 spd can handle?