Let me expand on that thought.
Of all the 12 port heads made back in the day, not one uses current varieties of chamber design, given here in order of technology:
1. 4 valve, pent roof
2. hemi
3. multi-angle, quench (BBC, Cleveland, 429)
4. wedge, closed chamber, parallel valves, quench (almost everything else from 1955-70)
This means that an engine built using these heads will produce less power than any modern design (Atlas, Barra, 2JZ, Ford 300).
