351C valve cutouts

Just wondered if anyone happened to know how many cc's the valve eyebrow reliefs in the top of a 351 Cobra Jet piston displace? These are the standard flat-top pistons as originally fitted. The engine is still together.
I wanted to work out possible compression ratio on one of these cr calculators, but I don't know the cc's of the valve relief cutouts.
I'm looking at replacing the big 4V open-chamber heads with a pair of Australian-made CHI 2V aluminum ones, which can be made with a variety of chamber sizes (64cc, 66cc, 70cc). I want to end up with 9.5-10:1 if possible.
Anyone have any experience of these heads?
Thanks guys,
Chris