I would like to add a couple of thoughts having towed with my even by 7.3L truck standards a sub HP 7.3L version (dynoed at 200/400 back in 2002) now for almost 15 years and close to 75K miles towing at a GCW of 16 to 17K. I have the 4.10 and even smaller tires than what came on the F-series, but even those owners that tow seem to agree with me that the really sweet spot for "serious pullin" is in the 2500 to 2600 rpm range in direct drive. For me I even approach the more serious clumps pushing 3K, however, for me because of the lack of an intercooler and crammed engine compartment I'm seriously EGT limited. Power has never been an issue, it's just those darn temps that make me have to back off on the longer pulls.
I don't have an exhaust brake, but with my super tight, BTS custom tuned tranny I have found even the puny coast clutch helps me some in the hills and I've towed all across the U.S. thru all the major mtn ranges fron the Sierras and Rockies out west to the Cumberlands, Smokies, and Adirondacks back east. The key is speed and proper gear going down.
Larry
