"How many OB chances (out of 104) are required at the top for a * lead-off man? I'm going to say 38-40 as a minimum."
I agree with this, 38-40 (out of 108) as a minimum with hopefully higher. I'm not a fan of speed except in pitcher's parks on a team with good pitching so that eeking out a run due to speed can be important even though trying to eek out that run risks an extra out being made. If it's a hitter's park or my team in general has heavy hitters I don't care much about speed and especially stolen bases as taking advantage of that will often just give up too many outs.