Wow. That looks different then any Schwinn one piece BB shell I've ever seen. Mine have all had a clear shot through the BB shell. I've converted two Super Sports, a Continental, a Twinn Sport (with 2 BBs), and knocked the cups out of a few Varsities and Collegiates and never seen that ridge. Weird!
By any chance was this a Shimano front freewheel Schwinn?