Stay away from Poly or plastic spacers.
How are your front springs? Sagged?
If your springs are good then I just suggest washers under the spring. You really don't need to weld them together. I've driven 20,000 on a set of unwelded and no probs. Plus this adds the added benefit of adjusting the ride heigth by adding or removing washers.
Now if your springs are shot, then new springs would be best. A set of skyjacker 132 springs would be your answer.
Now remember, with this said 2" is about the limit, even though on 2wd's it's more like 2.5". If you go past this alignment will be about impossible.