Assuming the compression is correct for those pistons on an 88cc head, then bumping the cc's down to 84 would give you a half point of compression or so?

This would probably get you into the high 9's with 84cc heads and the thinnest head gasket you can find which is fine for pump gas.

I would recommend you buy a set of 84cc Eddy RPM heads which will give you the desired compression rise. They will also be more tolerant of higher compression on pump gas than the traditional iron heads.

As far as 700hp out of that motor...that is pretty optimistic for this build naturally-aspirated. I am guessing he meant to use a blower which would explain the lower compression. I would guess you would be anywhere from 400-425 hp with the build you described and a good set of Eddy 84cc's and good intake/carb/headers/etc.