TB size for S-trim 5.0L recommendation?

[84_GT350]

I'd go with either a 70mm or a 75mm. You've got two things to consider. One would be the size of the opening at the inlet to the intake. A TB bigger than the inlet really isn't going to do you much good. If anything, I would think the air would get backed up there if the TB was too big. The second would be the driveability. As the TB gets bigger, part throttle applications will become much more touchy. For the same throttle application there will be quite a bit more air coming into the engine vs. a smaller TB. Obviously, with a blower this will be even more true. And how in the world would you ever fit a 90mm TB onto an intake? Hehe. That's like a damn manhole.