Do a search here for body bushings. There's tons of discussion, a lot were answers to my questions when I was doing it then advice I provided based on my experience. Take your time and be careful not to drop the car on yourself. Use a bunch of jack stands and a couple of floor jacks. If you take out the front seats you can reach the rear nuts for penetrating oil. You will also have to do something with the steering so you can separate the frame enough to get the new bushings in, either disconnect the rag joint or loosen the column and the steering box bolts so they can move around.