Apparently the BKP 550k pots are very good, but I haven't tried them yet.
You're right, I think Gibson use that 300k/500k setup on most guitars now. I haven't bothered to look what's in mine (and one is a semi, so I'm not going to try to take the pots out! :lol: )
What Junior have you got, by the way? Singlecut or doublecut? I'm a big fan of Jrs. :D