I think I found the part that would replace the manifold and allow a second water inlet (Newty got this at his local HD). Orbit changed the size of all their unions and connections and stuff and my Lowes is carrying the new stuff. According to one seller on ebay the old stuff was actually made by Dura and isn't available anymore from Orbit -- or at least they aren't "making" it anymore. Here's a link to a seller that has it:

http://www.sprinklerwarehouse.com/30.../301-010-3.htm