A jack and plenty of blocks will do the job. Not the easiest way but it can be done. Place wheel chocks,(blocks)in front of and behind the front tires. Jack up one side 4-6 inches safely block it on the frame just in front of the rear leaf spring. Move to the other side jack it up 4-6 inches block it on the frame just in front of the rear leaf spring. Keep doing this until you have the frame high enough to reposition the rear axel. Going too high in one jacking can cause the vehicle to slide off the blocks and **** someone so be extremely cautious.Using TWO jacks, one on each frame, and jacking them up at the same time or a cherry picker centered on the rear with the legs extended as far forward as they will go and the boom(hook) retracted as short as it will go would be better. either way you do it as clearance allows insert blocks under the frame to catch the truck with minimum fall in case it drops.