"Yeah. I only let it hit 70 once, when I wasn't paying attention. The 5.4 loves to run. If I don't hold it back, it would be doing 75. It seemed to get it's best MPG at a dash over 60. It has the 3.55 rear. "
I have 3:55's as well and when towing cruise at 59. Have to agree that the 5.4L loves to run. On the long grades of 6 to 8 % that often run for 10 miles or more out here I just put my foot in it and 3600 gives me max (365#) torque. Once in a while I may even see 4,000+ as I approach max HP (4400), but other than burning a bunch of fuel the engine has no complaint. It will hold about 1600 - 1700 rpm (59 mph), in OD at anything less than a 2% grade which accounts for the good mileage. :C