Kevin,
When we ran the '87 Mustang ITB, we used a Lexan "chin spoiler", vertical, aft of the radiator...Original manufacturer's concept... and put intakes into it to feed to the rotors. That was the simple part.
The best we could do was to "aim" the tubing at the center of the rotor, since the steering arm and the sway bar end were in the way of any meaningful duct attachment. A cleaner approach would have been from the rear of the rotor, but that was virtually impractical.
We found the cooling to be very important on short tracks, and actually fried the backing plate of the pad, and welded one plate to the piston.
Quality pad material was very difficult to find for the 4cylinder cars.
Yes you can take air from the surface of the air dam, and cut holes thru the valence to reach the rotors.
It's not mentioned, but remove the dust shielding from the inside of the rotor.
Good racing.
Bill