I've just gone thru something similar adding B4V spring spacers which work fine. Just compress the original springs, remove the original packing at the top of the spring and insert the spacer. For the shocks I used B4V shock extensions on the front and Martin sells extenders for the rear which has the effect of moving the shock away from the spring. Thus you don't need to buy new shocks.
I found that the original castor correction bushes (KAP) didn't work so well with the new lift so I used new front arms from Off Road Armoury, and put the original castor correction bushes in the rear arms to try and correct the diff angle.
Manual VVT, 2 1/2" lift, ORA castor corrected arms, 2" ORA body lift, 4:1 transfer box, Uprated front shafts & CVs ERM , ARBs back & front 3.9 diffs, 6 point cage, ORA winch bumper - Superwinch EP9, ORA rear bumper, ORA axle truses, Diff guards ERM , TBR tank guard, Snorkel, Kumho KL71.30.9.50 15
