Intake manifold help

G’day everyone,

I am swapping my old 318 manifold over for a new Edelbrock Performer.

When I try and fit the new manifold the bolt holes on the manifold don’t line up with the ones on the heads (about a third of the hole out). I am guessing I need to machine the new manifold but how do I know how much needs to come off?

Cheers
Anthony

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