Yeah i agree with the other posters. L98 heads are good but they run flat tops. Zero deck is fine but your pop ups are not the right kind. You need the ones that only pop up on the valve side. Regular domes wont work. Sounds like your pistons are standard dome for large chamber heads. They are made to give 11:1 not 14:1.
Since the squish band will be screwed it will knock like crazy even if you retard the timing and put in good gas. 110 will not fix it.
You need pop up pistons made for 58cc heads they are completly different shape. They can give you the same cc's without grinding anything. If you cut the heads you will trash the heads and still have to replace the pistons.
Buy cast iron 76 cc heads. Some stock ones flow very good and are very cheap because everyone wants to run flat tops or dish for large cams and lets face it. It is hard to check piston to valve clearence so nobody does it. Cause if you run flat tops and smalller lift cam it works fine.
If you want to make the 302 scream it will need compression and High lift cam. Without the correct pistons the valves will hit long before the cam is big enough to hit the 6k rpm power peak you need.
11:1 and a 250@.050 or bigger with high lift and tight lobe like a 106 or 108 12:1 would be even better and will work with 110 octane fuel.
And yes if your going for super high compression you can usally cut 1/4 inch out of most of the head area. Use a stiff wire to check the water jackets and try to measure up how thick they are. You can take a little more out of the head flat surface area across from the vavles but be easy around the spark plug area its pretty thin.
Proform i think makes aluminum heads dirt cheap in all port and chamber sizes. They are not the best but flow good and at about 700 a set complete its hard to beat. 76cc chambers and 210cc intake port should be real nice since they are all about the same price.
Sorry for the long post hope this helps.
Last edited by hcompton; 10-17-2012 at 05:11 PM.
Reason: Forgot to add the inch after 1/4