Hi blam,
I'm under the impression that the GBU-28 is the same "Bunker Buster" that we are using today, unless they've added a GPS guidance package in addtion/instead of the laser guidance and didn't re-designate. As of 1998, we had 125 in inventory.
http://www.fas.org/man/dod-101/sys/smart/gbu-28.htm But if I'm wrong, oh well. I'll get over it :)