I'm trying to upgrade an older Schwinn tandem that I found in very good condition but with not so great components. I'm presently occupied with installing new cranks, replacing the old, steel cottered cranks. I've successfully swapped out the stoker cranks, but the captain's is proving to be problematical. It has a cast aluminum eccentric that fits into the front b/b hanger, secured by two pinch bolts on the bottom of the shell. The shell is 73 mm wide. The eccentric fits flush on the left side, but protrudes 5 mm on the right side to provide a tab with which to rotate the eccentric for adjusting timing chain tension. I've tried fitting a 73x122 mtb cartridge b/b, but the extra 5 mm on the right side of the eccentric moves the spindle too far to the right. Does anybody have a suggestion as to how to deal with this...?