I bought my 89 T5 for $350 off of Craigslist.
It is also recommended you change out the rear bushing and seal. It is also a good idea to change the aluminum bearing retainer to a steel retainer. Here is how to do it: BM Ripper Shifter and T5 upgrades | FordMuscle Magazine
I got my Tremec 3550 off Corral.net classifieds, there are a lot of late model guys there and there always seems to be an abundance of different kinds of parts available at any given time.