Its usually not so much the springs that break, but the metal hole that they attach into stretches and breaks.
There are not enough hog rings in the seats to warrant a rebuild kit.
Remove the back of the seat from the base (removing the adjuster and the pivot on the other side) and there are clips holding the seat fabric on the base. Once those are free, you can pull the cover off. It velcros to the foam, so you can either remove that, or take the foam and the cloth off in one shot.
If the springs are ok, the foam might be pushed into the wire mesh type thing that holds the foam up. If it is, you can put a piece of cardboard (beer box unfolded) on top of the mesh and under the foam to give it the support. It needs to give a bit, but the cardboard will prevent squeaks.
Most of the Ford vehicles in the truck vintage run the same springs, so if you need a spring, most any seat can be a donor. If you need a new foam, Aerostar seats are a very close match. They are not exact, but there are usually a million of them at the wrecker.
Here is my old post on repairing a seat, except without the pictures, its pretty much useless
Ford Seat Rebuild