I keep seeing bottom brackets that say they are for 68/73 shells, how is that? I don't understand.

The only problem with the mr. whirly is that I'm worried about chainring selection... I'm not mountain biking, I'm riding on the street with a gear ratio of something like 50/20.

My question is what is wrong with going 144 on the Karate Monkey? Is it just that it's hard to find 125mm BB spindle lengths? Or is it that putting a 125 or 127 mm long BB on a bike with track cranks will look mega stupid and be prone to breakage?