back in high school i had a 85 ranger with a 351w and 36'' swomps all on stock running gear. D28 / 7.5, I never once broke any thing, and i wheeled the shit out of it ,its all on knowing how to wheel it. know days i would put different axles under the rig. but i would say 33'' - 34''s, i would be more concerned about the d28 well befor the 7.5