I'd probably skip the ITB's jusre because they're more hassle than it's worth on a boosted setup.
I'm not really sold on block guards either, i'd almost rather have a stock block. I think you're going to need a good tune to keep it together at 450hp on stock sleeves. It's not impossible, but i've heard the d-series have a tendency to move and pop the head gasket.
I can't remember who, I think Comp Cams, but they have a boost specific cam. Just go with the stage 2 because stage 1 isn't going to do much (and a lot of people report good gains with stage 2).
If you're going to put down those power levels you should also look into a LSD. I recomend the OBX (after you take it apart and put it together right). If you don't want to put that work in, a Quaffie is what it's a copy of and those are assembled right.
