Gosh, I bet they squeak a bit! Obviously a dire lack of rear end maintenance. Before anything else, I would give everything a clean up, lubricate the springs along their length where accessible with motor cycle chain oil spray, check spring shackles and pins are free to move and make sure that shockers are not seized. Then give the rear end a good few pushes up and down to see if it settles any lower. Lowering blocks may still be worth considering if no improvement. I have no direct experience of a 4/4 but it does not look right somehow.
