Thinking outside the box

Machined,

Good point.

What I have read is that true Hemi heads, like the early 241 Dodge engine in '53 and the 331 Hemi Chrysler motor introduced in 1951 (hope that's right!) were excessively expensive to manufacture because of the double rocker shafts and the sheer size of the heads (necessary because of the valve layout and valvetrain.)

The Polysphere wasn't a bad idea, to have an almost hemispherical chamber with only one rocker arm shaft, but the heads were still wider than a true wedge, with all the valves in a row, and the Polys didn't apparently flow all that well.

All the early Hemi motors were also VERY heavy for their displacement, mainly I think, because of all that necessary iron in the heads.

They (the Hemis) were great drag racing engines, for sure, but Chrysler didn't see the necessity of staying with that cylinder head design in the face of all the practical considerations, or so it wouuld seem.