My opinion is the D30 would be fine for what your describing. I would leave it open or run a selectable locker. I run 35x13.50 currently. I havent had any problems and I climb everything that looks like a challenge. HP D30 front and D35 rear with yukon axles and spartan locker. I have the 8.8 for when the 35 goes but it hasnt yet... I think auto trannys are a lot easier on differentials as well.
91 Laredo, 4.0ho, TF999, Magnaflow exhaust, Yukon rear axles, Spartan Lockers, Posi locker, 3.5 inch springs, 1"MML, 1"BL, 1"shackles, trimmed fenders, raised flares, 35x13.50s.