Under a heading of "For what its worth"
I some how got on the stock drive mailing list (I suspect I filled out an oline form at thier web site . They sent me several catalogs that have been very instructive on gears, thier uses and why I don't know enough about them.
There is still time, I suspect to order your own set.
http://www.sdp-si.com/
was the site I used.