Because my hood scoops are aftermarket (Mopars by Crane (now out of business)) I measured & documented each scoop's stud holes center to center. With those measurements I then used AutoCAD to create a stud mounting template for each scoop. The under hood bracing has 3 holes (if I remember correctly) per side that I center punched small pilot holes which each template was then lined up with.
I had the twin scoops on my hood for a few years before I built up the nerve to make them "functional". I purchased a set of the hood scoop grommets from DetroitMuscleTechnologies.com. I used tape on the top side of the hood, taped some plastic to the underside of the hood (to collect the metal shavings), drilled a pilot hole and then used a 4 1/8" hole saw.
I would suggest using some scrap material and different sized hole saws to get the perfect match for the grommets you plan to use!
And now they're "functional"!
Then a few years later (2018) I had my buddy, Trent, apply the gloss black paint (V21 style) to the hood, scoops and cowl.