Horse Power Potential of Cylinder Heads

I agree with absolutely everything you said especially the comments about flow test and dyno results. I'm usually a skeptic when it comes to guys and shops chest thumping and touting those figures and all that's why.
But I don't agree with this: " (these will support no more than 497 HP)"
If one builds a combination that is highly efficient - not just in airflow but in combustion and limiting pumping and frictional losses - you can exceed that number. Such an engine in a V-8 factory-type package is a compromise in terms of longevity and costs, but that figure can be exceeded fairly significantly if you control the things that work against power getting to the crank hub. That's the line of thinking behind any successful Stock Eliminator engine builder and many FAST class builders.