I don't know the answer but the guys that do are gonna ask what size track you're running and maybe if you run mufflers or not. My guess is 1 7/8"-2" if you're running a 3/8 or less. Also banking can matter since it effects the corner speed which effects your low RPM range. If you don't mind I'd like to know if there's really an advantage/disadvantage to forward swept headers over standard other than just to fit those big Cali style mufflers. Hope I didn't run on to much