A rear trac bar drop bracket for a 4" lift will work. That's what I have on mine, I think the brand is full Traction.
Also I have never heard of ZJ coils giving that much lift.
Like I said my BDS 3" springs were $109 for the front and $119 for the rear so not that expensive.
Also Full Traction, BDS,Rusty's and a few others sell a complete 3" kit for $500 or so.