1. The Stillen SC for the 370 has had a rough history on here, search through the FI section and you'll find the threads for it.
2. If you're looking for 400whp, your better off getting the GTM Stage 1 kit as the Stillen kit never reached that point if I remember correctly.
3. With a very simple, slight modification to oil pressures in the AT, it holds the power just fine. Confirmed for both SC and TT applications up to 500hp and then a little more. A TT 7AT with the right tranny mods is dangerous.