I repair Rusty Frames and I probably would not fix that one. Its a lot of damage. The frame is the easy part to fix. Its the body that's bent as well back to the rear door. The frame would have to be cut out and replaced as well and plated back together. The corner is mangled and probably bent the floor along with all the supports on that side. So when someone would pull it back all that bent area will rust and rot 2 to 3X faster then normal. This is why the other members suggested to put the parts into a non rear end damaged one. :-(

Not to mention, if that section got hit again it would crash a lot worse because all that steel is really severely weakened.