So, I just moved into a service truck and I'm still trying to get her all figured out. She's a 2001 f-550 w/ 7.3l and low-hole 6 speed overdrive. All dressed out and ready to fix stuff she ways bout 15,500 lbs. When cruising in the highway when you get to 65 mph the engine is turning 2500 rpms. It will run 70, but 65 just seems smoother like that is the sweet spot. I got past the other day by a tire truck that seemed identical, just different bed, he had to have been doin 70+. A guy from one of our other stores said in his old truck (set up pretty much the same) he just held it to the redline (governor) and let it fly. He claims his held up a long time, but I'm pretty skeptical. So... my question is, how many r's are too many and how fast will these trucks (sanely) cruise at?