I've encountered a similar situation several times when putting mountain bike cranks on touring bikes. Using a shorter BB fixed the chainline problem. Use your old crank to determine the your current chainline distance. You can do some measurements using your current BB and new cranks to determine the axle length you need to get close to the current one. You don't need to measure the exact chainline, just the distance from the center chainring to the down tube. Measure the distance between old and new cranks, multiply by 2, and subtract from length of current BB axle.