Ok, on the head there is no need to cut it past the gasket ridge. Once you cut much more you will begin to loose flow. Flow is more important to a flat head than compression. Also if you mill too much your valves could hit the head. So then you have to cut over the valves. Then you begin to loose what you did by milling. So You can angle mill the head also. In other words have it milled more over the bore area than over the valves to keep more room for flow over and around the valves. You rules say your cam must be .330 lift. no limit on duration. That means any serious puller is going to have a reground cam that is still .330 lift but with more duration and different lobe separation etc. You need something like this.
https://vogelmanufacturing.com/singl...ange.html.html
Notice that the cam specs are V338-245/338-238-3 That means once you have set your lash at .008 you will still be only .330 lift. Trust me when I say you need a cam like this. Most everything else is experience, and preparation for the stock class. Also you can advance your ignition timing by opening your points .022-.024 Good luck