I'm sorry I don't know how to add the direct link thing but
www.darkhorseperformance.com has a conversion kit and some of the lowest prices for the tremec I have seen.
You may want to try looking for some back-issues of Mustang Monthly for auto-to-manual conversions and then use the kit from whatever source you need. Darkhorse may also be able to give some technical advise.
Good luck!