They go between the frame and the body with a matching bushing inside the frame that the bolt goes thru, then thru the frame, and finally thru the bushing that goes between the frame and body.
In other words, there are two bushings for each location.
Seems like there are seven pairs per side. Probably a diagram on gnttype.org.
Look under the frame and you will see an excess hole thru the bottom of the fram about every three feet.
Not that hard to do but a little tedious. Have to raise the body a bit to swap them. Worse part is cars from up North that have the bolts rusted solid and the nut inside the body breaks loose from the welds when you try to remove the bolts. I suggest an impact wrench to break them loose.