Stock Willys hoods came with a built in air dam in the upper portion of the hood.  This airdam was made to fit down onto the top of the stock factory Willys radiator. both of my hoods were missing this item. When I installed my custom Ron Davis alum front radiator, I had Ron Batson of Batson's Metal Works of Santee, Ca make the basic air dam for me, which I added further additions hanging down from the basic air dam to close off all paths of air around the front radiator.