Thanks guys! A lot to consider that's for sure.
Based on your RPM range inputs, I found this calculator online and compared some of the options between transmissions/rearends.
csgnetwork.com Engine RPM Calculator
Based on the calculations, I'm inclined to stick with the 3.08 rear gear with the OD transmission for now. The 250 inline 6 is a high torque low rpm engine and I might get away using the 3.08 rear gears.
Worst case I'd have to drop it down into a lower 1:1 final gear which is where I'm presently at driving in town and at highway speeds.
Here are a couple of different rpm scenerios for highway and around town I ran for the .63 OD and 1:1 final ratios with the two rearend gearsets.
Again, thanks for the info!