Yes. Those be them.
I have templates for those to shape the chambers. Im gonna start selling them. They mount at head bolt holes and are reversible to do the flipped layout...but anyways..
They 'the 920' are probably around 66'ish cc as cast.
The portion of the chamber closed 'having no peak between the valves unlike 302 heads makes the % closed as less volume reduced. The open 318 head 675 are 68'ish cc on average as an example.
Thing to consider valve n seat grinds drop valves in the cylinder and chamber volume grows as a byproduct.