eric-
I can only echo what many who have made this swap say, "It's like going from manual steering to power steering." I have a '39 gear box in my '35 and would never change back. The car steers easier, the wheel self-returns after turning, easier to adjust and doesn't have the leaks that a '35-'36 gear box has. Go for it!
If interested, I can give you some further details. Rather than clutter up the board, send me a PM.
Tom