since you asked for block info... i would recomend going to an truck off road lift place and get the blocks. they sell the steel/metal blocks that will not break like the cast aluminum will. you might also need to adjust your pinion angle due to the the axle wrap that happens when you lower it this way.
Consider this...dearch the springs 1" and then use a smaller spacer to fine tune the ride height to your liking. I would not recomend dearching 2" because if it is then too low your only option is to rearch or new springs.
The problem with a 2" spacer is that it puts the spring/shock plate too low...especially if your run Traction-Masters or some other type of traction bar that mounts on the bottom of the plate.
Most metropolitan areas will have leaf spring shops that typically service spring on large commercial trucks.