Gaara specs -
Gaara would have the full knowledge and the techniques that he had before being captured by Deidara and for the sake of the argument, Gaara has access to tailed beast transformation and the friendship of the first tails (being it is obvious that he would not be able to handle Killer B Without this).
Killer B Specs -
Full specs and knowledge from the great from the fourth great ninja war and being he had samehada that is included.
The terrain for this battle is going to be in a plain making it fair for both 'contenders', this plain is going to be identical to the plain where the Kimimaro vs. lee took place.[Only photo I could find with a clear idea of the image I was trying to make.]
I don't think Gaara has the necessary speed to handle Killer B. The sand he carries would not be enough to take down Killer B even though it was fast enough to block Amaterasu (which would be Gaara' fastest feat with his sand). He could always make more, but if Killer B went full Eight Tails off the bat then Gaara would be in trouble. If Gaara responded by also going full Tailed Beast transformation, Gyūki would still have the upper hand mostly since he can fire multiple tailed beast balls at once assuming their speeds and strengths are matched in this state.
Gaara would not need speed being he has all the abilities that shukaku has which also pertains magnet release, which derives to his sealing ability. Shukaku is able to seal anything his sand/himself makes contact with this includes outside sand which can be created from their combined abilities and on top of this he has the ability to make tailed beast balls. If Killer bee were to go into his tailed beast form he would be the one who loses to his ability to seal things he makes contact with, also he himself is made out of sand and he is the tailed beast who totes 'Ultimate defense' meaning he would be able to handle tailed beast bombs for the most part.
Shukaku's technique can seal targets upon completion of the technique unless you are referring to his natural Cursed Seals, which need a medium (such as sand or the Rasengan). Even so, sealing the target does not stop them from using jutsu as seen when Madara used his Susanoo to escape from Shukaku's jutsu. If that's the case, Gyūki can still used Tailed Beast Balls to break free from the technique or Killer B can use Lightning Release to break out of the technique. Shukaku can use Tailed Beast Balls, but not at the same rate as Gyūki unless shown or stated otherwise. Also, if Madara can break through the sand with a Susanoo sword (which was only in its humanoid stage) after the sand was already enhanced with Cursed Seals (and it was part of Shukaku's body), wouldn't a tailed beast ball easily be able to blast through Shukaku's sand? Even Gaara's sand wasn't able to handle a chidori. I doubt it could withstand a Tailed Beast Ball or several. Gyūki also survived a Tailed Beast Ball from the Ten Tails, so I'm not sure Shukaku's would do much damage to it.
madara already activated his susanoo before the seal was complete. and that was Madara, you can't in any way shape or form compare him and Gyuki. a perfect susanoo is as strong as a tailed beast, but is used by a shinobi who can better use said power.
and the sand of Gaara that was damaged by a chidori was young gaara's sand. kage Gaara's sand is on an entire different level.
not to mention Gaara has more than just Sand, he has magnet release, wind release, earth release and lightning release.
to be honest no ordinary lightning jutsu is getting through his sand. bee doesn't have a chidori.