If the main reason for tearing into this engine is to raise compression and the pistons are going to be replaced, I'd take it one step further by replacing the crank & rods with a 302. That will increase displacement and help raise compression.
As far as deck clearance goes, don't guess, measure it. Piston to head clearance is critical with quench type heads.
The Power SqueezeYou should be shooting for a .035-.045" distance max. So if the pistons are .015 in the hole you should be looking for a .030 thick head gasket. If you want to run a .045" gasket, the block should be decked .015-.020.
That should get you pretty close to 10.5:1. If you still need more, then you can cut the heads.
