I have 2003 year in class c. Can't give you exact RPM's that mine runs but never had a problem. 10,380 pounds leaving driveway. I just let motor do its thing and keep oil clean trans in "drive". On steep downgrades sometimes I take off O/D. You do have to understand and keep up on the plugs (one of Fords better ideas). I have well over 100,000 miles. Many people get 250-300 k miles. If you have auto trans, that is the weak point IMO. Forget about winning any races or fuel mileage.
I've been told to expect the engine to run at a very high rpm but this engine was made for that and can handle the high rpm.
YA it does run high but sings along, no problems.
So those who have or had this engine how did it handle oh I also have 3.73 for rear end.
I have 3.73 also.
I know a diesel would be better but this is what I have and have to live with it for a while
We've also got a 01 Dodge 5.9 turbo diesel, that we tow with. They are booth about the same, I get up to 65mph and drive along. In Dodge I can really here Cummings doing its thing, wife calls is the "back hoe" motor. In 5.4 triton we call the "sewing machine" motor. They both will get you there.
P.S. I us only the Motorcraft filter because of silicone ring that keeps oil from draining out of filter, so that every start is not like a "cold start".
2003 Majestic 23P... Northwest travel machine
2013 Arctic Fox 25W... Wife "doll house" for longer snowbird trips
2001 "The Mighty Dodge"... tow vehicle for "doll house"