LS 71 chevelle swap, input needed

[highdrum]

Everyone has been a great help thus far, I have a few more questions........installing a 416 LS3 with LSA supercharger(750ish HOPP) 4L80E trans
1. What flex plate should I use for this kind of horsepower
2. Wanting 1-7/8" long tube headers, whats the best/affordable option, have looked at stainless works as well as musclerods, all 800$+, using dirty dingo sliders
3. I have read that there may be minor clearancing for the trans to fit, but not much, what the best mount? I have seen aftermarket mounts for the 4L80e that are notched for exhaust.
4. Plan on running 3" exhauast, willl this interfere with the trans/cooler lines? Or will the flowmaster setup go right in?

Thanks for any help, I am sure I will have more questions later! This is the beast thats getting the swap!