FWIW (not much) my Trooper, with manual transmission, 35" tires, and 5.38 gears is turning around 3300 rpm at 75 mph. But here is the point - I still get 15-16 mpg at that speed on a lifted vehicle that was only rated for 17 highway by the EPA in stock form. And these DOHC engines aren't strained in the least by running that high of an rpm all day.

So I don't worry about it.