New heads?

Yep.......... here is another.

Iron vs. Alloy Engine Heads - Tech Article - Chevy High Performance Magazine

These two were the only tests of the same casting and air flows that I ever found.

Anybody else found anything similar?

Oh, excuse me for awhile, I must go elk hunting!
Those are what I have seen.....I can't recall anything else but I can well have forgotten. Neither test was perfect but their conclusions were the same.

IMHO.... the broad statement in the first article of 'heat kills power' is the kind of broad statement that gets misunderstood and misinterpreted as to the specific's of why. I would expect it is all in the heating in the intake tract that lowers density, not in the chamber after the valve is closed.

Good luck with the hunting, Jim! Man, I wish I was there... I would be your 'gun carrier' and call you 'Bwana' LOL