Only had time today to try this and it didn't work for me, probably because the axle had too much load on it. So I started from the beginning and found this solution worked for me. I've only tried it on the rears as I'd already fitted the fronts independently of each other but I guess the method would work for those as well.
Rear Leaf Springs - How To
1. Loosen 3 shackle/chassis bolt nuts (23mm) and 4 U-Bolt nuts (19mm) either side.
2. Spray WD40 penetrator (or similar) on the rear shackle/chassis bolt threads
3. Loosen wheel nuts both sides;
4. Jack up axle, place axle stand or similar under chassis towards the front of the landie just past the leaf spring chassis bolt on both sides.
5. Remove both wheels
6. Lower jacked up axle to just below normal height.
7. Place another jack under the a leaf spring plate. Jack it up until it’s taking the load.
8. Undo 4 U-Bolts or cut the U-Bolts themselves if a nut is seized. I had to cut one out of four U-Bolts.
9. Slowly lower the jack under the leaf spring plate. remove Jack and plate.
10. Remove the top bolt only (21mm) on the rear shackle plate and lower leaf spring to the ground. Should come out quite easily. Use a jack under the leaf spring near that end to take off some of the load if necessary.
11. Remove the front chassis leaf spring bolt and lower leaf spring to the ground.
12. Drag out leaf spring and remove shackle bolt and the two plates still attached to the leaf spring.
13. Place new leaf spring under the landie and offer up to the front chassis eyes, placing a jack or wood under neath might help. Give it a bit of wellie to line it up with the bolt hole. I sprayed the bolt with WD40 after wire brushing the threads before sliding it through the hole.
14. Push the two rear bolts into the unthreaded shackle plate and pass the lower bolt through the rear leaf spring hole.
15. Lift the rear leaf spring up and pass the top bolt through the chassis.
16. Screw the top bolt into the threaded shackle plate, not too much. Then screw in the bottom bolt into the same plate. Tighten up alternately until the plate is nearly tight.
17. Place the lower plate under the leaf spring and jack it up towards the slightly lowered axle.
18. When it gets close to the top plate (brake lines attached), stop and wiggle plate until it slots over the leaf spring pin.
19. Jack it up further until it touches the axle. Now play around with the axle until it clips onto the leaf spring. There should be a lot of play at this point, however you may find that the axle is slightly skewed, it will twist until it’s almost flat. Jack it up a bit to slot it home.
20. Fit u-bolts (should be about 1.5cm of thread visible through the plate) and bolt on nuts but not tightly, just take the bolts upto the plate.
21. Lower the Jack slowly.
22. Repeat steps 7-21 on the other wheel.
23. Loosely screw on the shackle/chassis bolts nuts.
24. Jack up axle on one side. Fit wheel and wheel nuts. Remove chassis stand on that side. Lower the jack.
25. Repeat 24 on the other side (i had to jack up both sides separately to get the wheels on, can’t remember why).
26. Tighten all the wheel nuts.
27. Do your thing about settling the leaf springs and tighten all bolts and nuts.
