I might just fill the second plug hole with modeling clay.....should get me pretty close.

I assume by cc'ing the heads you want to determine what the CR will be with and without the head gaskets?

I have C2 Turbo cylinders and according to Porsche, the engines had a cylinder head gasket. When I resealed the engine back in 2002, I installed the heads without the gaskets because they weren't there when I tore it down. I have some minute weeping between head and cylinder, which was symptomatic on some of the engines. Porsche put head gaskets on those engines, I believe, to help seal between the two surfaces. Don't know if I am going to have resurface the heads, but I want to be prepared for whatever I encounter.