Amount of lift is pretty debatable, I'm running 39.5s with no lift when you should really only run 38s. That extra 3/4" gives me a rub when near full stuff on a front corner, even though I built shackles that are 1-1/2" longer than stock...roughly 3/4 lift as the rear spring point stayed stock.
Anyway, I'd go at least 3"....even then, with a softer than stock spring, you may have to extend the bump stops to keep it from rubbing under articulation.
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