[olddog]

I rarely drive on an Interstate highway. Yes the .64 is great when you do, but the huge step between 4th and 5th is annoying to me. There will always be a road condition where 4th has the RPM too high and 5th makes the engine unhappy, if you have a performance cam. If you have a large displacement truck engine, with low end stump pulling torque, it would make a great cruiser.

I would go with .82 5th. If I wanted the rpm to come down at highway speeds I would step the rear end ratio down. If that will kill too much low end, then go to a 6 speed with a .82 5th and a .64 6th. I doubt a big block would need low gears.