Factory HEMI Head!

Maybe so, but read My edit above...........................
I see the edit.
Those heads are about as desirable as tits on a bull.
The B/RB is covered by Hemi heads. I'm sure his heads were things of beauty, but the market for something like that would be less than tiny.
Aside from the obvious bling appeal of a Hemi Slant, there is a very real flaw in the engines that this could turn around.
Because of the long stroke, long rod and small piston area, the Slant is doomed to always be a slug down low.
They don't wake up until around 3 grand, when the speed of the journal swinging past that dead TDC zone better matches the pressure wave.
Then, just as they wake up, they flat run out of cylinder head. This is why getting any reasonable return in terms of performance on a N/A Slant is so dismal.
Now, with a high capacity cross flow head, the concept of Slant performance can be completely rewritten.
Imagine a 9 or 10,000 RPM 170 or hybrid 198 Low Deck in a sub 3000 pound car with a clutch. You are talking world class modern performance out of a basic engine that can be had for scrap prices anywhere in the country.
There are probably close to a million of them still out in the wild.
This idea can have some serious legs