[supereal]

I agree with placing the frame on stands, then using a floor jack under the ends of the spring to release tension on the shackles to remove and replace them. If you are removing the spring assembly after the shackles are off to work on it, be sure to use a new center bolt when you put it together, and orient the head of the bolt parallel to the spring so it will enter the hole in the cross member. We use a couple of big "C" clamps to hold the spring while the bolt is tightened. Those springs have a lot of power, so be careful.