Magnums aren't better, they do have a closed chamber and on some flow bench somewhere as stock flow 3 cfm more @.300 [1.94 vs 1.88, but at all other lifts flow less than an LA head. Then they also have pedestal stud mount rockers, thin castings that crack and don't have much potential ported form beyond 250 cfm, meanwhile LA heads hit 270-290's cfm on an average when ported, just bowl blended LA heads flow 240's on the intake.
Those who say they are better need to show me their flow #'s stock and ported.
The magnums beyond stock don't even get close the old heads.