With my lift (OME HD/Rancho, 3/8" top plate spacer, no clevis yet) I've got Duratrac 245/75 R16 on cragar soft 8's, which as said have 4" backspacing. The backspacing and the larger tire both increase the arc in which the outer edge swings. I had to pound the pinch and trim the bottom 1/3 of my bumper off (or at least the wheel well) and I still rub in reverse when turning one way. Soon I'll get a zip tie or two and hold the wheel well a little farther away. Then when I do a front bumper I won't have any problems.
Long story short: the 4" backspacing + larger tire = trimming
Personally I like it trimmed, love the wider stance, and it will give you a little added stability. Totally worth it.