I finally got around to it today. I've had all the parts put together for some time. My objective all along was to do a small lift ALL AROUND (I prefer the rake look). I did the PRG lift on the front awhile back, which gave me between 2" and 2.5" up front. So I chose 2" on the rear as well, and added 2" untapered steel blocks, flipped and upsized the u-bolts (to 5/8" Grade 8), and got new shocks. I flipped the u-bolts because I think it gives a cleaner look to the rear axle.
I built the blocks myself using two pieces of 6"x2.5"x1" thick steel plate welded all around, plus a 9/16 solid rod welded down the center to act as the centering pin. I got the steel from a contractor for free as a favor, so other than the time cutting and welding, these were more or less free. I think I may have paid about $1 for two 4" long 9/16 bolts, which I cut off the head and threaded portions of to make the 9/16 centering pins.
I had the 5/8" U-bolts and 3/8" thick spring top plates custom made to my specs for $86 delivered, by these guys:
http://www.customsuspension.com/Products.php . I welded the factory bump stop to the new top plates (since it previously clamped on top), as you can see in one of the pics.
The shocks I went with are Rancho RS5000, part #RS5269. They are 16.5" compressed, 27.25" extended and 10.75" travel. Rancho lists them for the rear of '99-current GM 1/2-ton 4x4's with a 4" lift, '02-current Dodge 1/2-ton 4x4's, Hummers, and a couple of others. I got them from Summit for $87 delivered:
http://www.summitracing.com/landing/truck/ . The tops fit perfectly. On the bottoms I had to use two 9/16 washers to make up for the slightly narrower lower bushings.
A note on the factory off-road rear shocks: They are TOO SHORT from the factory, even without a lift! They only extend to 24". When I jacked up my truck and first let the axle free-hang before disassembly, they supported the axle. When I took them off, I found that the axle will hang a little lower (to about 25" between shock mounting eyes). Keep that in mind if you are doing heavy off-roading. If you are doing even a very small rear lift, you need new shocks.
I will post pics of the overall truck in a few days once it is clean, and its not raining outside. But here are a few of the parts close-up.