Widest Duster tire?

Tell me more about this "offset shackle kit"?
Pictures of the front hanger and rear shackle to offset the spring 3/4" inward.
You have to move the spring perch on the rear also.
I looked these up on Summit, and can't beleive how much they want for these, or the spring relocation kit. What the heck are they thinking

hanger.jpg

shackle.jpg