Welcome to our home!
If your going to go forced induction, you may not want to mill the head that far. If you've already got a high overlap cam, it isn't going to work optimally with forced induction anyway.
First you need to find out where you are starting from. Pull the head and cc the chambers. Find out how far down the hole your piston is, and work up the compression ratio based on the particulars for your engine.
The most bang for the buck in a normally aspirated engine build is going to involve cutting the head to some degree. Since these engines aren't large displacement, you will need to balance all things together to get the most out of a build. It's not as forgiving as starting with a 400+ inch monster that will produce lots of noise and torque even when it's not built to the right combination.
Building a Turbo and/or FI motor is a very complicated process that will take at minumum lots of time, and more than likely lots of money.
Guys making more than 300 hp out of these engines have a lot of time and dollars bound up in them. The 500+ HP jobs are beyond the realm of the average home machinist. I'm going to be pushing $3K for a little under 250HP. Keep that in sight before diving off the high board.
Visit the Articles section of this site, and you'll find lots of information about various builds and power adders. Running a search on a particular method will also access more information. Have fun!
CJ