David,
That's something we here at World have wondered too. There's also a near-nonexistant response to our aluminum block and head announcement I posted a few days ago.
I'm not sure about all Cobra chassis designs but one issue I can imagine is fitment in certain cars. I know that "Cobra Jeff" here has a Cleveland or "Clevor" in his ERA so it can't be too much of a factor. Another possibility is the height of the CHI intake, especially with a .250" taller 4500. On Windsor-style heads, the CHI is 1.5" taller than a Vic. Jr. and 1.125" taller than a Super Vic. Only a modified scoop will work on a Cobra and many owners may be reluctant to do so.
A related issue may be the fact that Jon is a "one-man shop" and makes very small volumes of castings per month.
We have built and tested a "Clevor" here with CHI's heads on our 9.5 deck Man O'War and it made an easy 625 at 460 inches
with the wrong pistons. We will build this crate combo when refined, I'm told. See pic below.
As a side note, World is casting the CHI intake for our Windsor-style heads with availability in the Spring.
I would think that these heads (or our brand-new 6-bolt heads with LS-style ports) on our aluminum 108Lb. block would be very desirable for Cobras or GT 40's. I don't think price is too much a factor here.
