The entire body is held onto the frame with bolts that go thru the body bushings, and mount plates/brackets. I think 10 on a BII...
If your body bushings are toast, you do need to replace them. Depending on how bad they are, you might be able to go awhile before doing so. In my experience, the steel tubes inside the bushings tend to rust out, and may contribute to the mounts themselves rusting out. I had two mounts rusted out, and ended up welding a steel plate on top of each to replace the damage. I did try very large thick washers to cover the rusted out holes, but they didn't really work.
Sometimes you will have to either brake the bolts, or cut them, as they tend to rust solid in my experience. (even with liberal amounts of penetrant oil)
A decent body lift kit should come with extended bolts, an extension for the motor ground wire, and an extension for the steeringwheel shaft. You may need to make or buy extension mounts for your radiator. (I just used a couple of pieces of heavy gauge steel strapping with holes drilled to mount.)
Almost all the work envolved in adding the body lift, is being done while replacing the bushings.