You have an asymetrical BB. Assuming the 40mm is on the drive side, you'll need one that is a 137mm (that is the measurement without the threaded sections). One with crank bolts instead of being nutted is fine (and most likely what you'll be able to find). Number of bearing is important but some of that depends if you have a carrier for the bearings or use loose bearing. You can usually get at least one or two more balls in without the carrier. I doubt the shop lied, more likely they were just ignorant of all that is out there.