Is there a way to merge Lib A to Lib B, using the .XML file in the itunes folder?
How about the .itl file?
and the com.apple.itunes.plist one??
and symply manually copying all of the 867 folders containing all the music into Music->itunes->itunesMusic??
Copy the files where you want them, and add them using File > Add Folder to Library.
If you end up with any duplicates, delete them.