[Tinker]

Well I don't know what all is going on here. You will need to use a spring spreader to remove the shackles. (you have to take the vehicle weight off the rear by jacking up the rear on the frame and putting some jackstands on the frame, didn't think I need to mention that. But you never know) Once those are removed the spring has a center bolt to keep the spring pack together. So the u-bolts wont make the spring come apart.

If the center spring bolt is not broken then the spring can be released from the ubolts holding it in the cross member. I guess when loosing the u-bolts on the cross member you might see the spring separating then you might have a broken spring pack bolt. I have not seen that personally but it's possible. But really if that happens, the ubolts are long enough. But take caution.

Once the spring is out you can use a couple big c clamps clamped to the spring pack to remove the center bolt and take the spring pack apart. Take your time to do it slowly and allow the pressure to release. It sounds worse then it really is, but it is under pressure.