I have always read that the Hemi combustion chamber is more detonation prone
and needs more octane.
It's the exact opposite of what you have read. The Hemi has the most efficient combustion chamber shape of the era, and a centrally located spark plug. The flame front has an equal distance to travel in all directions from the spark plug. That reduces its octane requirement.
Aluminum heads help a lot also on any motor to reduce detonation on pump gas
There is quench in all Hemi combustion chambers as long as the piston has a dome that is above the block but not like wedge motors have with one side having it and the other side under the combustion chamber not having it
I use thin narrow strips of clay on the hemi motor pistons to check piston to head clearances on my high compression builds, check that out to see about quench clearances also
