I've installed a couple with no problems, a couple that were just about ok with some fiddling, and a couple where I've measured up and told the owner forget it, let's do a B7. In practice, on 330s/Casinos sometimes a B3 works and sometimes it doesn't - it depends on the neck pitch of the individual guitar. The reason is break angle, if there's not at least a little over the bridge a B3/B6 won't work for because a top mounted ABR style bridge is typically low to the body you're likely to run into problems.
When Gibson first introduced the 330 they offered it with a B3 rather than a B7 but switched to a B7 within 18 months or so, probably because they couldn't consistently get the B3 to work on them. The rule of thumb is if the bridge is raised up off the body on a wooden base, use a B3 or B6, if it's directly mounted onto the top use a B7.
