Here is the vent I was talking about. I am going to be trying something similar on my spare hood for my 70 El Camino as a radiator hot air duct, I want to find a spare set of fenders, I just can't bring myself to cut into mine.
Front fender vents - Chevelle Tech
They are a simple enough design, and can be made to look great depending on your design and how much you like bodywork. These could look downright cool on a Mustang!