I won a set in a raffle, & ran em for 2/3 season: Sold them in VGC for $75.
I can't recommend them... Mine never did 'unload' really violently during hillclimbs, but just knowing that they could made me much less confident. (I've enough issues on my junk to fret over without adding another thing to babysit)
IIRC they were good for approx 5/8" lift over stock XJ shackles, but that will depend alot on where your spring eye sits.
My vote: save the $75 or invest some into tuning the leafpacks for better function if they aren't doing what you'd like.