I've been thinking about doing the same thing on my 58 Viking 60. (big 6 lug). I would probably leave the OD unit in straight through until I got on the freeway so, it should not add many more shifts than what I have now. A more modern rear with taller gears would work as well (especially if you found one with the right bolt pattern, and possibly a 2-speed!) and also may give you brake drums that you can still buy if worn out! The one advantage the ranger unit would have is your speedo will still be correct (assuming it is now).
