Well, Dave is running 9s in his '67 Chevelle (which I presume is lighter than your Monte) and all it took was a 760+hp 509ci engine.
He sells a kit to build one (you just have to add your intake, carb, and oil pan) for a little under $10k.
As I type this I'm building my shelter to protect me from the Itty-bitty-Engine Brigade(e.g. Small block owners), but I don't see how you could conceivably (let alone safely) get the kind of HP you're talking about, let alone withstand the boost/nos you're planning, with a warmed over 350. I just don't think the block itself can take that much abuse.