Dual Hood Scoops Functional
On a '66 you'd be totally on your own for placement. The '70/71 hoods come with holes in the understructure of the hood (the holes labeled "1" in the picture I posted above). Those holes work well to locate the scoops, and the large holes are 4-1/8". On the '70/71 cars the holes are not centered under the scoops, they are at the front and toward one side.
Making the holes larger would create some issues, mostly because there is a rubber gasket that is made for those holes to keep water out of your engine compartment. The gasket has a tall lip on the side that goes up, so water running back on the hood into the scoop stays out of the engine compartment. The gaskets work well if the holes are close to 4 1/8", but if you went much larger than that you'd have to come up with your own gaskets.
On a '66 you'd be totally on your own for placement. The '70/71 hoods come with holes in the understructure of the hood (the holes labeled "1" in the picture I posted above). Those holes work well to locate the scoops, and the large holes are 4-1/8". On the '70/71 cars the holes are not centered under the scoops, they are at the front and toward one side.
Making the holes larger would create some issues, mostly because there is a rubber gasket that is made for those holes to keep water out of your engine compartment. The gasket has a tall lip on the side that goes up, so water running back on the hood into the scoop stays out of the engine compartment. The gaskets work well if the holes are close to 4 1/8", but if you went much larger than that you'd have to come up with your own gaskets.