Can anyone tell me what the difference is between a 350 turbo and a 400 turbo transmission? Basically, I have a nice 350 turbo, but someone said I might consider upgrading....I will be mating it to a 350 small block, if that helps. I don't have a rear end picked yet, so I'm open to suggestions there too! I want good off-the-line performance, and good acceleration up to highway speeds. (as opposed to my BMW M635, which is sluggish off the line, but has a sweet spot that's far in excess of the legal speed limit!).