The holes on the dual pattern intakes do intersect, but there is enough material to use as a guide to mark it, or even a guide to drill the front and rear holes. Once those are drilled and tapped, a simple flat square stock with tubes can be fabricated very cheap and easy to use as a guide.
If you are buying an LA intake anyway, set the intake in place with gaskets, line up the ports, and use the LA intake to mark the heads.
Here is pic of the head-side of a dual pattern intake showing the intersection.
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