The highways around here are ~70mph almost constantly if you plan on getting anywhere, tollways push 80. Obviously you can go as slow as you want, but my biggest annoyance with 3.91s was the constant screaming of the engine just to maintain a reasonable speed...hence the double-overdrive 6spd that now resides in my garage.

If I kept it with a non-OD, I would have put 3.23s in it and putted along, I was done and over with running low gears on the street.

At 3,200rpm instead of 70, i'll be at 110! 70 at 2,000.