The  rear spring tower that you see here is on a RATCO frame and it is the same spring tower that is included in the Spring Tower Replacement Kit.   As with the Rear Differential Replacement Kit, you can install this structure without removing the body from the car.   It comes assembled except for one of vertical supports or pillars.  The procedure is to remove the old spring tower structure and prepare the area for the new unit as per the instructions.   The new springtower assembly  to is slid across the width of the chassis and after using a special fixture supplied for exact placement, the unit is welded in place..  if the body is off the frame, we can make the tower complete and all that is necessary is to drop the structure in place, use the alignment fixture supplied and weld.. 
This procdure is a weekend project.  Not at all hard but you will need to cut off the old and weld in the new.  You need the tools and welding knowledge..
 
As with the Differential Crossmember Replacement Kit,  this kit is also suppled with  a set of rail covers that wrap the chassis rails with new steel and allow welding of new to new steel. They do a great job of strengthening the entire area as well.   The kit comes with all new hardware and a detailed set of instructions.