X vs J- flow differences?

PRH said
On my current bench, and my previous bench...... in equal condition...... X heads outflow J heads.
And with equal amounts of porting, the
X heads still outflow the J heads.

The X heads have a superior intake floor and SSR.
They are not “the same” heads.

Taking one of each in ootb form, by running my finger down over the intake SSR from the bowl side, I could easily tell which was which while blindfolded.
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It would be interesting to find out what the engineers at Mopar did to create the casting differences. Next time I see Radar (Roger Luctenberg) I will ask him if he did any porting for the OEM. I know he was on the B1 team and when he worked at Gary Ostrich's shop they did experimental work for Chrysler Corp.