Replacing the FSB on using taper pins isn't a do-it-yourself type of job unless you're a master machinist.  Manufacturers use a jig to align the FSB to the barrel, and then drill the holes into the assembly.  Thus, the holes aren't in the exact same place from barrel to barrel, and duplicating them in a new FSB takes the right equipment, plenty of skill, and patience.  Oh, and a jig also helps!

Since you're probably just trying to add a bayo lug, I can tell you that it really isn't worth doing.  You'll spend AT LEAST half the cost of a replacement barrel to get a new FSB installed, and then what?  You gonna bayonet someone?  Probably not.

Currently, there are no clamp-on FSBs, but someone will probably figure out how to make one.  If such a thing is made, then it would be significantly easier to do-it-yourself.

-Troy