As you can see in the mid 60's onward the forward down slope classic spoiler was what i call the "first generation " of aerodynamic engineered additions. And they do work. Allthough to be effective and measurable they must operated at those higher airspeeds. Later wind tunnel testing has shown that the flat or more vertical mounted front air dam directs pressure wave up through radiator. And to left, right around fenders. This change in shown in later trucks, tahoes as the flat extension below our bumpers. But, but...as a kid in high school in 74 the Camaro's, Challengers, 'Cuda's, Shelby GT 500. So freaking cool.