hey guys... I am sure this topic has been beaten to death but ive been spending a while on multiple different forums including this one and haven't seen a list of parts that should be replaced at certain hp levels... if there is one can you please post the link if not please educate me as much as possible!
I want to put a 200-4r in my car but my certain financial situation is not gonna allow me to do that. So i figured I would consider rebuilding my current TH350 that is in the car. My dad got it from a late 70s caprice I believe and sometime in the early 90s installed a b&m shift kit into the trans.... other than that it is stock.
Soon I will be dropping in a 355 that should be making around 400 hp and 400 tq. I was wondering what I should do to the trans to make sure it lives. The trans is good right now shifts hard for every gear... from 1st to 2nd it engages the seat belt locks

I have a 3200 stall redneck racing converter along with a deep aluminum vented pan and an extra cooler up front. I figured I would start with the basic rebuild of clutches, seals, gaskets.... Is there any hard parts that I should have to replace? any suggested kits? I wouldn't mind keeping the shift kit in it now... but whatever you guys think will be best. Thanks in advance!