Well.... I have a confession to make.
I have a TH350 behind my BBC (hey, it came w/the car). Fact is, it has served me well so far. I have been concerned with constant abuse however. I like that it is lighter & easier to spin, but I do believe I need TH400 & I am exceeding the HP for my application by 50HP according to my trans guy. I figure I will see how she does, then go 400 after that. I wonder if I will need to modify/change my x-member & drive line for the TH400???