whats the difference between a add a leaf and rear blocks im looking at a 2inch RE budget boost

 

Add-a-Leafs are a single spring that you add to your existing spring-pack for lift, and increased payload capacity....blocks are nothing more than a thick spacer between your axle and the spring pack. I'm no XJ guru by any stretch of the imagination.....but I see blocks as a bad idea all around.
Seperating your axle from the springs is just asking for a malfunction, that block will add increased pressure on your U-bolts.
Myself with my new (new to me) XJ....I'm waiting to stockpile enuff money away so when I want to lift, I can buy 4 brand new springs that were manufactured to work with one another, and the kit that they come in will have everything needed to support the modifications I want.
Add a leaf gives "instant gratification" but if your stock springs are any kind of weak....which they probably are....in the long run you'll be disappointed with the results.....hope this helps.....Scott

 

I agree you should really stay away from both and get new leaf spring packs but if you can only get one or the other i would stick with a long AAL rather than a short and just stay away from blocks