I had the opportunity about a year ago due solely to my own fault to have to drive a 650 mile day home from the stove bolt get together .
By coincidence it was the same distance to the event the only difference being I had an over drive gear that kept the rpm on my stock 62 235 at around 2200 rpm. at 70 mph.
the trip home with no overdrive had me traveling at around 60 mph give or take and a fairly constant 3000 rpm. The only difference I noticed is that it pulled up the hills without lose of speed or the need to downshift. The truck weighs in at about 6000 lbs, and has the aerodynamics of and apartment building . I check mpg with every fill up and fuel mileage remained the same at 14 mpg. in both directions. Both trips were done none stop other then many MANY stops for gas.
I noticed no difference in temp. oil consumption or engine noise.
That being said I will be returning this april. along with new overdrive gears.
John
