Using an NV4500 with a .73 overdrive ratio and 30 inch tires, your engine would be spinning 2615.5 rpm at 70 mph with 4.57 gears. The overdrive gives you an effective ratio of 3.34. On paper it seems to work pretty good to me.
John
P.S. I just put a NV4500 in my 59 1/2 ton with 3.90 gears. I still have the low end grunt with the 5.61:1 first gear, and dropped cruising rpms down to 2480 at 70 mph. I have 27 inch tires. Taller tires would drop the rpm even further.
