Yossef,
I totally agree, I am first trying to identify the porting styles in general and more specifically whether the particular cb750 head I have was plausibly ported by Yoshimura as was suggested possible by the seller(as 3rd owner of engine, 1st owner reportedly spent a pile with Yoshimura in the mid 70s, it had a hand bent Yoshimura stove pipe race exhaust and a set of Smoothbores 29s on it at the time that Ted (Ricky Racer) has kept.
Knowing whether Yoshimura stamped the parts they modified would be a great help too. That was common back then(RC Engineering, etc)
George