Here is a little secret we'll let you in on. The first run of Kenne Bell 5.0L kits will feature billet intake manifolds. Kenne Bell did this to speed up production until the castings arrive. One won't flow or perform any better than the other-the billet aluminum lower manifolds will just add cool factor. Note the size of the throttle opening in the upper Mammoth intake manifold-it looks like it could literally swallow a wooly Mammoth.