In a small bowl stir together paprika, black pepper, and onion salt. Place ribs in a shallow dish. Squeeze lime halves over ribs and rub with cut side of each half. Sprinkle with spice mixture; rub in with your fingers. Cover and marinate in the refrigerator 1 to 4 hours.
Meanwhile, soak 6 to 8 oak or hickory wood chunks in water 1 hour.
Prepare smoker according to manufacturer's directions. Pour water into water pan; add wood chunks. Place ribs, bone sides down, over water pan. (Or place ribs in a rib rack; place over water pan.) Smoke, covered, 3 to 4 hours or until tender.
Meanwhile, for sauce, if using dried chipotle peppers, soak them in warm water 30 minutes; drain and finely chop. In a small saucepan stir together chipotle peppers and remaining ingredients. Cook and stir over low heat until heated through. Before serving, brush ribs with some of the sauce. Pass remaining sauce.