AB,
Cars are , "personal". That's what keeps us customizers in business. Like I tell all of our clients, do it your way.
As far as adding the new vents, naca ducts, etc., any body man that is capable of installing the vents can certainly make the necessary flanges to hold them. This would not be a major challenge and would / should look like a factory installation.
Another option would be to actually mould the vents in flush. It would eliminate the dirt / wax catching seems, and really give the hood a smooth and professional look.
Just another free opinion
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DV