^^

What he said.

Also, never stack blocks. As far as price, you'll need the blocks and new u-bolts, so figure around $75 and an afternoon of your time.

Add-a-leafs are about $100 a pair, and you'll also need new u-bolts to install these. Figure about $125-150 to do it this way.

BTW, about air shocks, I wouldn't recommend them. When filled, they're going to make the rear ride harder, and also put stress on the shock mounts. (just my opinion!)