Pick a speed, say 65 mph. Now, pick a gear ratio and tire size that puts you between 1800 and 2000 RPM. I think you'll find that 3.42 is going to be close to optimal unless you are grossing 10K or more. 3.03 is going to put you below the most efficient range, lugging if you will.
The Constitution needs to be re-read, not re-written!
If you can't handle Dr. Seuss, how will you handle real life?
Current oil burners: MB GLK250 BlueTEC, John Deere X758
New ride: MB GLS450 - most stately
Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510