I'm gettin' ready to do a lift on my burb, and mine will be getting new springs in the rear for a couple of reasons.
* My old springs are pretty tired now.
* Will avoid the dreaded spring wrap that I read is so common when running blocks in the rear.
* Can then shackle flip to attain any added lift to level the rear out, if needed (8,600lb burb, and will be getting some added running and storage gear).
I have tossed around about every scenario I could come up with on lifting this thing. And even if I had good springs presently, I would/will go with new ones front and rear for the above reasons. Physics says the farther you separate the axle tube from the spring itself (blocks), the more leverage it has to wrap the spring under acceleration and deceleration. Sure, lots of people out there running ridiculously large blocks, but that doesn't always make it the best way to do it. Just the cheapest and easiest. And I'm all about having things done right, and done in a manner that will least likely cause problems down the road (or trail).
I am far from a 4wd guru, still learning this stuff myself. But a fair amount of research and learning from more experienced people than me has shown me that there are better ways than just throwing blocks in something. Food for thought.
As for the pinion angle, there are angled shims you can buy to reset the pinion angle. But again, with blocks too, that, to me, is a scary proposition.
Someone else will chime in here soon and let us know how far off I am in my thinking on this.