Get the fiber ones. I have had both and the fiber are better. The brass feels way too stiff. It takes a good 1/2 hour of driving before the tranny is warmed up enough to make the shifting any smoother. The brass also crunch on quick shifts becasue they cannot create enough friction. Go with the fiber ones, and make sure to use at least 4 ounces of Fords Friction Modifer or Trans-x differential addative in the tranny (Ford said the Posi Tracion Trans X addative will work fine).