From my reading, the gearsets from gen 3 to gen 4 were the same (or close enough to call them the same). The gen 3 sho had diffrent gears, providing LESS low end torque (geared down less) because it had more low end torque than the vulcan and duratec, and did not ned it (unless your Paul Nimz :lol2: )
Paul did a gear swap in his sho from roughly 3.77-->3.99 (i believe, correct if wrong). He had issues untill he got the PCM tuned for that gearset. Id ask him about it.