Here is what I have so far on leaf springs:
OME CS033RB - 4" lift springs - 52" eye-to-eye flat length as quoted by ARBUSA
OME CS033RA - 3" lift springs - 52" eye-to-eye flat length as quoted by ARBUSA
Rough Country 8047D - 4" lift springs - 52.5" eye-to-eye flat length as measured by me on two pairs
Iron Rock Offroad - 3.5" lift springs - 53" eye-to-eye flat length as quoted by IRO
Based on my measurements, the IRO leaf pack, which is the longest XJ-specific spring that I have found to-date, will clear the rear crossmember when using a straight shackle that is 4.75" eye-to-eye (which is what I currently have). So I have yet to find a leaf pack that needs a boomerang, but I wouldn't be surprised if the Deaver leaf pack needs one. I called Deaver a few days ago, but I didn't ask for the flat length because they told me that the spring rate was north of 200 lbs/in which is more than what I want.