The problem you will have is, you can't shut the vent. If you use a aircleaner with snorkles with the hot tube valves, you could rig them to open when the cowl is closed. If they don't shut, then you have hot air anyway. I would go with the tubes under the headlights. Insulate the tubes and you are good to go. You also need to ride in a truck with the cowl vent open to see just how much air you really get. The freshest air is in front of the grill, not over the hood. Check out the real fast race cars, the scoops are out high above the hoods well in front.
Before I put a scoop on my race car, I taped sticks on the hood with small flags on them. The only air that was really moving was 8-10" above the hood about 3" back from the grill, and right at the base of the windshield. The difference between a car laid back windshield and a truck straight up windshield is a lot. The air may not be where you think it is.
This would be a cool modification, but the logistics of making it work may out way the coolness.
Just more to think about, Joe
