Look at the position of the spring shackel to see weather it is in the same position on both the drivers side spring, and the passenger side spring. (Note): you should always install the spring by bolting the fixed eye to the body first (the front bushing on the spring). I installed the shackel end first once and got the same problem. I drove with it like this for about 10,000 miles to find that it was wearing my tires all crazy like. I also always had a slight pull to the right that an allignment couldn't fix.
This may or may not be the problem; however, it sounds just like the problem I fixed about 3 months ago. I purchaced new OEM leaf packs. I got the heavy duty ones that you get for the off road towing package in an XJ. I'm about to get a 3" AAL and ditch the blocks. Blocks are BAD for leaf packs!!!!!!!!!!!!!!!!! I have been through 2 sets in 3 years.
Brian