...and what's wrong with lowering the bb? And don't bring up the old "pedal strike" argument: In 35 years of riding (including 15 years of USCF racing) I've caught pedals on the pavement maybe half a dozen times, the last one was um.... let's see.... 15-20 years ago. And that includes a lot of miles on a bike with a 10" bb height and 180mm cranks.

SP
Bend, OR
ps - going from a 700x23c to 650x38b (probably the most common conversion) will drop your bb 5 mm (< 1/4"), not 3/4".