Setting aside the fact that drums are a pain in the backside to work on, you might ask if it is really an advantage to do the conversion. Some would argue that the friction inherent in the disk system could be considered a cost, in terms of speed, and that the drums provide all of the braking that the rear wheels can handle, anyway.
I think that the master cylinder, parking brake cables, and other bits are different, I think, so the swap might require more time, hardware and $$ than might first seem to be the case...
Just a thought.
Kirk