I have been slowing my 10.70 car down to run 11.50s for the last ten years. I had been using a Moroso bolt style system that bolts to the right rear carb stud and is adjusted out or in , it restricts how much they throttle opens. I have been pretty successful with this setup. I recently went to a Willys adjustable restrictor plate that moves in and out via turning a screw, it goes between the carb and manifold like a spacer. So far i only made one good pass and went 11.40 but the track was too cold to hook any other runs last Sunday.