"As mentioned it will run all day long at 4 - 4.2k. Just watch the temperature. As long as it's not climbing any faster than the gas gauge is dropping you'll be okay. "
LMAO, Now that is funny!
I have to agree with everyone else here, put your foot down and go. My V-10, like the 6.0, loves to rev. I get max torque down low in the curve at 3250 but max HP happens at 4,400 and frankly it just isn't all that loud. Be sure to engage your Tow Haul (or lock out OD if you don't have T/H), as this will shave 10 or more degrees off of your trans temps due to more efficient cooling.
:C