I can show you several pictures of 302 blocks that have split in half from the cam tunnel down, all around the 500-550hp range. I wouldn't trust one to a large amount of boost or a large amount of naturally aspirated horsepower. Guys like to run valley girdles and main girdles, but all they do is keep the pieces together when they split....ROFL
The aftermarket blocks will take a pounding, but the factory blocks are a crap shoot when it comes to strength.
I've never been a forced induction kinda guy and have always preferred naturally aspirated engines.
How much would a turbo/supercharger kit run you that would put out that much boost? Would it be cheaper to do a stroker kit?