To the OP, I agree with those who say a 10-46 w/ a 56 for the low B. I use these for my B tuned and Bb (B flat) tuned guitars with no issues at all. I would avoid trying to go with sonething really heavy like a 64 or bigger, unless you really wanna replace the nut from grinding that huge ass string back and forth in it... I've had to replace the nut on all of my guitars that were bought used because prior owners did just that. Using something way bigger than needed wears out your nut after a while (on a fixed bridge equipped guitar, Floyd Rose style trem equipped guitars don't have that problem due to a metal nut...) and turn the action at the nut side to shit.
on the matter: 10-56's Regular Slinky 7's, with a proper intonation and you should be good.