Many lock out 6th gear when towing with the 3.42s. Helps the trans stay alive and keeps the engine temps down.
I like driving fast, but when using my girlfriend's 2500 to tow the 911 pictured earlier, it was a bit fast even for me in 6th.
In my 3500 with 3.73s (and the shorter DRW tires), it does 80 mph at 2,000 rpm, which the engine seems to like, and it's my preferred speed.