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You got me there.
Is it possible that someone has drilled & tapped the cylinder head for the extra studs?
I ask because i have never known of this pattern on a round port head before, & i am assuming, rightly or wrongly, that the center stud [hole] is in this head above & between the "pairs" of round inlet ports, giving, in effect, a dual pattern.
I had also always believed that this stud pattern was created for the oval port head, to provide greater support & to ensure more even clamping force around the increased circumference of the oval ports.

Tell us more, as you have my undivided attention now. This has got to be a rare one. Do you have, or have you seen, the round port manifold that goes with it?