the front spring mounts & the ladder bar front mount are at different lengths from the diff so as the suspension rises or drops , the arcs are different so you need a 1-1.5" slot in the spring mount to allow the diff to move on the springs , you can easiy make them using a steel plate above & below the spring & use spacers & grease the heck out of them , the ladder bar transmits the power the spring just hold the body up , I have never found anything better for traction , I used to pull the front wheel on the street @ stop lights using street tires