There's a guy that frequents (or at least use to) another Pontiac site, who is considered an expert in transmissions. He owns http://www.jakesperformance.com/ and has building them for years. He only recommends the TransGo kits.

He follows multiple forums (all GM makes), so google "jakeshoe" and TH350 and you'll get a ton of hits. He has lots of great advice that he's shared with members that had questions, with some interesting tid bits and recommendation when using those kits. So read up first before you buy and install.