Jack the truck up and get it high enough that you can hold the front wheels at least an inch off the ground by putting jack stands under the frame. Since you are working on a BII it might help to back it up onto some ramps. That way you don't tip it over on it's behindus.
Then put a jack under the axle beam where the radius arm bolts to it, take the lower shock bolt out, and let the jack down slowly. Once the beam hits full droop you should be able to get the spring out. If you need a bit more space wrap a good ratchet strap through the spring and compress it a bit.