When I upgraded to a TH400 from a 2 speed I worked with Shift Works out of Las Vegas, they have all the right components. You may be missing some key parts. Very knowledgeable folks. My whole conversion was not very expensive and was an easy install. Resulted in less frustration, and very dependable conversion. I learned a long time ago using cobbled up parts is not the way to go. They are on the net;
www.shiftworks.com