Then last outboard BBs I've bought have simply come with two spacers for the DS and one spacer for the NDS.
For a 73 mm BB shell, and no BB mounted accessory, use no NDS spacer and one DS spacer.
For a 73 mm BB shell, and a BB mounted accessory, use no NDS spacer and no DS spacer.
For a 68 mm BB shell, and no BB mounted accessory, use one NDS spacer and two DS spacers.
For a 68 mm BB shell, and a BB mounted accessory, use one NDS spacer and one DS spacer.
Does square taper do it differently? Haven't mounted one in awhile.