Here is a picture of the shackle assembly. Two bolts to the frame (note any shim placement) and two bolts to lock plates behind the seat (they thread In from underneath).You need to use a penetrant oil on them as they get gummed up over the years and will snap.
https://www.flickr.com/photos/advance-design_parts_co/8129483565/in/album-72157631868452754/They will need new rubber most likely but you may find it is collapsed because your front mount is bad. Look at where the pedal shafts come though the floor if the holes are egg-shaped or rubbing you have a bad front mount. This is very common on AD's as the floor gets all the mud and snow over the years (usually on the DS).
Here is an illustration of how the system works, the cab is mounted at four points and when the front sheet metal and radiator supports are correctly installed they function as the fifth.
https://www.flickr.com/photos/advance-design_parts_co/11974011174/in/album-72157639819091033/
