I'd leave the CR alone and seriously investigate the intercooler method. That should be good for a safe 20% power gain. Beyond that you will need massive internal modifications that cost way more than it's worth. A guy posted details of how he pumped up a 617 a few years ago to somewhere near 200hp but he also said he'd NEVER do it again, it took hundreds of hours labor, and a disgusting amount of money (nearly $10k, IIRC).
