You can fabricate brackets that will bolt up a bar to the existing holes that mount the top of the shocks currently, or as most do, pick up the holes that mount the bump stops for the rear axel. I made extended bump stops and a shock mount bar into one assembly. Only hard part is working around the exhaust. The bar also creates a cross brace from one side of the frame to the other.....somewhat like a ladder frame.
Most people move the bottom shock mounting brackets up on the axel at the same time so they can size the new shocks one time.