Which head/combustion chamber is better for performance? Speed master aluminum LA or aftermarket magnum iron head?

LO23M8B said
Yes I have a set of x heads on my 340. 11.86 at about 3900 lbs. I built it to go 12.20's at 6000 and on my first run it went 12.20 at 6 grand. My friends were not amused.
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That’s pretty damned impressive at 3900 pounds.

On iron heads no less. PERFECT!