Expected chainline from 103 mm bottom bracket to 107 mm bottom bracket?
I agree with @Mac that you may not be able to tell the difference between 103 and 107. If your current 103mm is in good shape, why not buy the new crankset and try it on the old bottom bracket? Evaluate the chainline. If it's good, you are done. If the (front) chainring is too far inboard, buy the 107mm bottom bracket.