I'm skeptical of Chevrolet proving in the 60s the reverse scoop being best. If it's the best, why haven't car makers today adopted it? The main benefit to the reverse scoop would seem to be cooling the engine air.
Both the cowl induction and reverse scoop would seem limited in benefit because I don't see how they'd effectively pull air in. Scoops need to be tall enough to stick out above the boundary layer of the airflow. If they don't, then they don't reach the low-pressure air. Air at the boundary layer is slower, which you don't want--you want fast air. Which is why older WRX scoops were so tall and ugly. A general diagram would be this (granted IRL the boundary layer would probably be closer to the car):
Ideally an intake would draw from the stagnation point above the boundary layer. A reverse scoop would definitely not reach above the boundary layer, and the front-faced cowl from Gruppe-M may or may not. The only possible downside to the cowl as opposed to the reverse scoop would be flow separation and turbulence created from the scoop jutting out, but given its small size I doubt it'd have much of an adverse effect.
The other modding possibility would be to stick a NACA duct on the hood, which actually would be the best solution because it minimizes turbulence while allowing faster air to hit the intake, creating a ram-air effect. Either way, the ram-air effect wouldn't be felt unless you were going at least 50mph, so it's something that'd only really help on the track.