5.17:1 gear. Does that sound right?
5.43 and 6.17 were the factory options I'd expect to find under that truck. 5.17 is much closer to what was put under 1-ton trucks, though that number was 5.14.
What are you planning to run for tires? Tire height can make a big difference. And as Grigg points out, Diesel motors don't turn real fast so deep gears can severely limit speed potential.
Of course with that Brownie box you have some options that might help. It would be interesting to know exactly what OD ratio it has.
