Anyone interested in building a small mechanical organ should read the
Busker Organ Forum.  Discussion covers a broad range of topics and comes
mostly from active amateur builders: http://buskerorgan.freeforums.org/ 

The Wurlitzer 105b Yahoo Discussion Group has two articles by Mike
Schoeppner in their "Files" section.  These list several sources of
plans.  I'm not sure if you have to be a member to read them, but
in any case membership is probably worthwhile for any organ builder.
The forum focuses on the Wurlitzer 105 band organ family, but
circulates more general information as well.

  https://groups.yahoo.com/neo/groups/wurlitzer105b/files/Sources%20of%20Plans/ 

Wallace Venable