I rev out our 6.2L gasser in our Ford quite often when towing. For a while I would try to keep the rpm under 4500rpm or so but now that I have gotten used to the noise it will rev up to 6000 and hold there sometimes while climbing hills or merging onto the highway.
Ever since I have done that I am happier with the towing experience and power the 6.2 makes.
2014 Jayco Swift 281BHS
2015 F250 XLT 4x4 Crew Cab, Short box, 6.2 gas
Solar powered! The trailer not the truck!