I've looked through the forums to see how much lift they give, and found several different numbers. I realize it will vary, but I want the most definitive answer possible. So how much lift do they give?

 

i put a set out of a V8 grand cherokee coils (not the Up Country package) on my XJ along with a 2" spacer and it netted me 2" of lift...... lol it provides a better than stock ride, the coils i guess don't sag after they settle like original XJ coils do....

BUT if you find some out a V8 grand cherokee that has the Up-Country package you should get 2"

 

If I get spacers in addition to the ZJ springs, do they need to be ZJ spacers or XJ spacers?

 

either or.... an XJ front Coil spring has the same "bump stop tube" diameter as a ZJ front coil does..... the rears off a ZJ however i'm not sure about.... you could also "for the cheap upgrade" just go to a salvage yard and snag a few factory coil spring isolators of some XJ/ZJ fronts... if you take about 3-4 pairs and put them on the front (assuming they are in good condition and not all cracked out and blown) that should be roughly about the same as a 2" coil spacer..... lol it doesn't look the best but it will serve as a coil spacer lift until you can buy some coils or some actual legit coil spacers