I noticed that when I go to purchase Rusty's 4.5" lift kit with the 4.5" rear leaf pack (not AAL), they give you the option of going either a full 4.5" spring, or a 3" spring with 1.5" shackles.
Why is it that the 3" spring - 1.5" shackle combination is more expensive than the 4.5" full leaf spring? It seems to me it should be the other way around, but then again, I'm new to this.
Is there an advantage to having the shackle set-up?

Thanks.