One of the best factory shaker scoop designs was on the '74 Pontiac Trans Am I owned back then. It originally had a factory-blocked opening but all it needed was drilling out three rivets for it to be fully-functional. In case of rain all I had to do was put the original factory plate back in the scoop opening
The design was a rearward facing opening drawing cool air from the high-pressure area at the base of the windshield. The base of the shaker sealed against the underpart of the hood with a thick rubber gasket and there was a drain hose on the driver-side front corner of the base to drain any rainwater/carwash moisture away from the engine to the ground.
One more thing, the opening in any scoop needs to be a minimum of 30 sq. in. to be fully effective and let the engine breathe at full throttle.
