[WSSix]

I'll second Charlie's suggestion. Eaton blowers look great and perform great as well.

To build this engine to your power goals, go ahead and get forged pistons and better connecting rods. Go with 6.0 liter style heads. Ported 317 heads will work great and you can go with a mild port job to keep costs down. Get a blower cam and 1-3/4 primary headers and you'll make you goals. I suggest a head change simply because better heads would really help the build, and should you ever remove the blower, you can put 5.7 liter heads on the engine and regain your current compression. Your goals are easy. You can make this level of power with 8 psi no sweat. Hell, I've done it with 5.5 psi and LS6 heads.

EDIT: Just reread your original post and realized you already own great heads. Go ahead and pick up some lower compression pistons. Shoot for 10:1 psi if not 10.25:1 With forged pistons you'll be fine. Speed Inc is in Illinois and they can help you for sure if you're wanting to contact someone local for advice and maybe parts.