I have an old Trek 9700 mountain bike that I'm resurrecting. It originally had a square taper crank/bb that I'm replacing with a Shimano LX & octalink setup that's coming off of another bike.

I'm having trouble finding the right bottom bracket size for it. The original was a 113 spindle width, but when I bought an octalink 113 from my local Perf bike and installed it, the small ring on the crank jams against the bracket for the E-type front derailleur. When I tried to return it, the mechanic gave me some spacers to add under the BB to space it out. This seems sort of jury rigged to me.

Does anyone know offhand if my new crank/BB setup requires a different spindle length than the original, and how to figure out what the new one should be?