I know its a shackle reverse, meaning the shackles are on the back of the spring, on the pinion side... If it has to long of a shackle, as it not matching the geometry of the spring hanger. Wouldn't it push the rear of the spring down? And wouldn't that cause the angle of the pinion to drop towards the ground?
My bros Toyota has this problem, he put long shackles in the front and it pushed his pinion down...he had to get Axel shims.
Sorry for all the confusion and misunderstanding.
Amilla