I've read, and read, and read on trans lately. I read a lot of posts on the 3550's. A lot of people put them through hell and they hold up. I know two guys personally who run them behind 347's, one while spraying. That being said, the conclusion I came to was that a 3550 was not too much of an upgrade over my Z-spec. I would definetly go straight to a TKO. I think the T5 based stuff will hold up in a light car. My father-n-law made 570fwhp (low torque though), leaving at 8000, shifting north of that, on a G-Force T5. Car weighs about 2800 I think. Been running that trans for several years.