Holy crap that would be sweet!
With our 3.85 final drive and stock diameter tires we would be at 1700rpm at 55mph. Thats about 600 less than with the .717 5th. My festy would still have no problem with accelerating or hills with that gearing!
I managed 47.2mpg on the way back from MACG doing 45 pretty much the whole way, I bet I would have been well over 50mpg with a .545 gear. I would have been cruising at 1400rpm!
If only I had the time, money, a spare trans, and a way for this to be 100% reliable.