I think you’d find that the “better” porting programs for the 18* style heads wouldn’t have that drop off in the high lifts....... and the ex ports are way better.
I haven’t tested any of those on the current flow bench, but on the old bench, and as done for the 9:1 358” Busch motors running a 390 carb...... to the best of my recollection those were in the 350 range on the intakes, and the ex was in the 250-260 range.
One current off the shelf example:
($2600/pr at Summit)
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