Marin mtb turned tri turned commuter turned singlespeed, Haro Werks 2.0, Specialized Epic Allez carbon main tube built up for triathlons
I don't mean removing the BB from the shell, I mean removing the BB core from the cups. Apparently, the UN72 is the only Shimano BB that this is possible for. I'm building up an old bike that came w/ a UN72 and my LBS dude said that if I get another UN72, I can "pop" the core out and have a spare. I haven't had time to go back and ask how though. I figured that the Internet would tell me, but it seems that this is a rare case, so there's not much info available.
"Shimano UN72 With Phil Wood Rings
It happens that Shimano UN72 bottom brackets can also be used with Phil Wood retaining rings. The UN72 model is the only Shimano series you can use this way, because the other Shimano models have the right side threads machined into the cartridge body. "