I suggest you write down the WT references given at this Quotes site:
http://www.reexamine.org/quotes/admin-site-map.htm#beliefs
All the dates are listed in the right-hand column: 1840, 1872, 1874, 1878, 1914, 1918, 1925, 1975
Sadly, many of these early publications are out of print by the society. Makes one wonder what is shady in their own origins, huh?
Here's a good early publication, fully available online, "Millions Now Living Will Never Die!" 1920, Rutherford http://www.reexamine.org/quotes/millions/Millions_Coverpage.html
The most damning evidence about the Governing Body are written by a humble former member, Ray Franz. His book, Crisis of Conscience, is practically required reading for exiting Witnesses:
Crisis of Conscience by Raymond Franz ( Paperback - Jun 2002)
Some more links to the history of the origins of Watchtower doctrines.
http://www.catholic-forum.com/members/popestleo/jwhistory.html
The Wikipedia article is good. Note the diagram that places the Governing Body between members and Jehovah.
http://en.wikipedia.org/wiki/Organizational_Structure_of_Jehovah%27s_Witnesses