If it's a stock block, no reason to waste the money stroking it. You can kill the block with stock displacement and a turbo. Check the block casting to see what year it is - if it's 72-back, you can handle aboiut 750HP before it's ready to die. The downside is, though, if you want to run a hydraulic roller cam, you have to either buy expensive linked bar lifters or a reduced base circle cam. The newer roller blocks won't handle as much power as the older ones, but they're already set up to run a roller cam so you don't have to do any changing.
Static compression really doesn't mean crap when building an engine - the camshaft is where the magic really happens. However, if you're not going custom grind and want to keep things in the safe area, shoot for between 9:1 and 9.5:1 for a good responding engine.
I can't answer the last question, as I've never had my hands on an On3 kit. I will say that the head selection isn't quite as critical with a boosted setup as it is with an N/A setup, as fluids flow differently under pressure than under vacuum. I'd really like to get my hands on a set of TFS highports for my next engine.