Planning on 2200 - 2500 rpm seems logical for an ideal cruising rpm for I6 engine longevity, in an empty truck.
I'll agree with that for a stock 235, maybe a little higher rpm depending on what has been done to the engine. Mine (not stock) does fine at 2700 rpm on the highway, roughly 72 mph in overdrive with 3.90 gears and 30" tires.
