Depends on which driver you want to install. I recommend using
sbopkg to download and install the drivers you need.
For b43 you'll need b43 firmware and b43 fwcutter - both from slackbuilds (or sbokg).
You need to add the following to /etc/modprobe.d/blacklist.conf and then rebot:
blacklist wl
For the WL driver you'll need broadcom-sta from slackbuilds or via sbopkg and then add the following to /etc/modprobe.d/blacklist.conf and then reboot.
blacklist b43
blacklist ssb
I use broadcom-sta with the broadcom 4312.