BB Tranny

I need some advice, I have a 402 BB in my 67 camaro and currently have a th350 with a stage 2 shift kit and was reccently overhauled (so I was told). I work at a wrecking yard and have a chance to buy a th-400 for 100 bucks canadian. I wanna do this and put a master overhaul kit and manual valve body in it to beef it up. My engine is built and computer dynoed to a underrated 400 hp. Im setting up to run a 150 shot of nitrious and i wanna make sure my tranny will handle the load. Should I go for the 400 and what are some of the things I should know and look for and what parts would you guys buy to beef up the 400. thanks.