I've got a '98 dodge 3500 with a 12-valve cummins, NV4500 5-speed, and 4.10 rear gears. The 12-valve is governed at 2250 rpm but you can get a 3200 rpm governor spring kit pretty cheap. My engine turn ~2200 @ 65 mph and 2400 rpm @ 70 mph. Unloaded @ 65 mph it gets ~17.5 mpg and @ 70 mph ~16 mpg. Loaded it is usually around 13 and 11 respectively.

1953 3600 w/ full pressure 235
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