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Yes, as mentioned above, 4 and 2 WD steering gear boxes are different. One way to differentiate them is how the pitman arm attaches to the gear box.
A few photos showing 4WD pitman arm attached to steering gear box by a bolt in pitman arm going through recess in shaft, and tightening onto splines in shaft. The 2WD attaches pitman arm by a nut on bottom of shaft.