It depends on throat angles, valve job. Weather air swirls and follows air paths into the chamber or is very turbulent going into the chamber. As I said before, not good at explaining how this all works, I do know how it is supposed to flow into the chamber though
Sometimes, a valve will look like it is pinched off & is so close to the side of the chamber, you relieve the chamber wall & it does not really help, well that is because that is not the way the path of air/fuel is entering the chamber.
From what the ported guy did to the other cyl head chamber walls, it looks like a lot of airflow enters the back side (close to the spark plug hole) of the chamber. That is how my cyl head picked up a lot of CFM, but mine is aftermarket.
If that guy knows how to port those Pontiac heads & is rebuttable I would just try & copy his porting techniques. Or were you going to have him port it?
As far as compression goes, I would shoot for 8.5-9.0 compression ratio.
Again, not too sure you should go as big on the ports as the gasket is? Unless your flange is made smaller than the intake/exhaust gasket. Bigger is not always better.