Looking at the pics of the chambers, I would think that a couple of chamber cuts around the valves set to the confines of the 4.27 inch bore wouldn't hurt anything. Like Jas1062 said, with frequent trips to 7,000 rpm, keep the ring gap and maybe (probably?) the piston to wall toward the loose side. With Fel-Pro 1009 gaskets .039 compressed thickness and "close to 80cc chambers" (440 Source), your static compression by the summit calculator comes up to 10.47:1 with a zero deck height installation.
