I have a 3.5 inch lift on my 91 xj now and I was thinking about a little more height with a budget kit. Ik with even a 4.5 inch lift people use aftermarket control arms and if I were to put one in would I need aftermarket control arms. Also do I need to get blocks or can I add another ad a leaf

 

aftermarket track bar, lower control arms, 5" shackles (should be paired with full leaf packs aslo) for the rear to get to 4.5"
and if you want to flex at all, probably longer shocks and brake lines as well. depends on what you've already got
4.5" and higher is where you start to get expensive. do not use blocks under any circumstances