Here is what I found from my research, it isnt necessarally true, and I hope someone can prove me wrong, but it makes sence to me.
OEM's put the pass side shock in front, and the drivers side in the rear.
Have you ever taken a rear end out and tried to move it by turning the pinion? You may notice it wants to turn in a counter clockwide rotation.
Also, you have a centrifigal force from the driveshaft turning.
By placing the shocks in that fashon done by the OEM's you are effectivally reducing the 2 forces I just described.
BUT I think that setup doesnt help all that much when you have a spool or a locker that wants to push both tires forward at an equal force.