Did some side-by-side comparisons today with the CHI aluminum heads and my old Ford iron heads.
Because the CHI heads are brand new, and the iron heads have likely been milled some time in their history, definitive comparisons are subject to some qualifications when comparing the height of the threaded holes for the headers and intake, but it appears both have been raised to some degree, the headers most likely definitively raised even accounting for some iron head milling.
I still need to take photos of the performer manifold when the new CHI heads are bolted in place to see if it also displays a 0.270” gap as seen with the Blue Thunder manifold. Stand by for that.
But when it comes to the valve cover rails, there is no question that CHI has raised them by roughly 1/4”.