Seems to rely a lot on the combo. Paul did back to back dyno testing on a 500hp 455 with sd ported heads and Paul's custom hydraulic roller and the manifolds were within just 3-4 HP and actually made more average torque on that engine.
That engine was for a member here and there was a nice thread on it a few years ago with all the build details and the dyno sessions.
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2019 Pontiac Heaven class winner
https://youtu.be/XqEydRRRwqE
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