You can actually make a case for the Poly being a better head than the LA. I don't want to derail the OP's thread too far, but in a nutshell; the Polys were individual runner, straighter ports, better valvetrain geometry, and a polyspheric (some call them the "semi-hemi") combustion chamber. The width killed it for A body use (as previously stated), and higher manufacturing costs caused its ultimate demise. The LA heads were really just a compromise design to get a wedge head on an existing block architecture, and inherited all kinds of weird geometry issues and port compromises in order to make them work- but they've been the standard for sixty years now. Who knows where we'd be performance-wise if the poly heads had been getting some lovin' for all these decades instead of the LA heads... just food for thought.