[Aussie Mike]

Yes there may be similarities but did they copy?

I understand there are theories about the ideal intake to exhaust valve size ratio. To maintain that and have the valves fit in a particular bore size there are going to be a few that come to the same conclusion. Same goes for port volumes. There will be a formula that works.

As for exhaust duration many motors take advantage of the smaller exhaust valve size to leave it hanging open for as long as possible without piston to valve contact. Modern roller cams and a light weight valve train let you snap those valves open and closed amazingly fast compared to old tech.

There were plenty of other GM designs they had to draw from too. As an example Dart make a Buick head for the SB chev that uses the port design and shape from the V6. A style that looks very similar to the what the LS7 uses.

I believe these were the go to SBC head for a while in NASCAR in the 90's