On my 3/4 ton, I have switched from 4.57 to 4.10 gears. I also went from a 29" to 31" tire. This has dropped my rpms from 3,000 to just over 2,500 at 60 mph. The only problem with running the taller tires is the truck sets higher, which some people don't like. I'm running 7.00X15 front and 7.50X16 rear. The fronts are the stock size for the 3/4 ton.
Running an unbalanced 235 at high rpm for extended stretches is not recommended. Over time, the rods will fail. While I have turned 4,500 rpm on a few occaisions, I recommend 2,500 rpm to be the top for cruising. A fully balanced engine has a red line over 6,000 rpm.
