Hey Wedge, Usually when I run into this situation it deems easier to
use a thicker head gasket,and/or to mill the combustion chambers out in the cyl. heads. to the required cc. Also you only have to set up 2
heads versus setting up 8 individual pistons in the vise. Another thing to keep in mind is when you mill pistons, this will change
the bobweight of the rotating assembly, and thin quench pad.
Cometic will make any thickness of head gasket to your spec if not shelfed.If all else fails, order custom pistons and wait 2 weeks.
However you hash it out, I would try to retain a squish factor of
around .040 - .050 for optimal volumetric effiency.
Hope this info can help. GOOD LUCK!