the rearend will move a little, but if you have worn out original rubber bushings its going to move a whole lot more. as far as not being square, do you mean it sits to one side, or is the housing turned? there are a few things that can cause that, but new control arms might just solve both issues. plus upper adjustables allow us to move the rear to one side or the other since they are what locates the rear.
yep those are the ones, but as you can see they are pricey. id buy the uppers and look somewhere else for some lower ones that are cheaper. the axle mount side of the currie uppers is a little beefier than the edelbrocks, but if youre not running 500+ hp, i dont see why they wouldnt suffice. just make sure you put rubber bushings back in the housing so you get a little compliance.
also, id talk to tobin at kore3 about a brake setup when you are ready. i originally bought the cpp stuff, but wasnt really happy. i sold it and went with the c6 z06 stuff. tobin has a few different options, but the c5/6 setup is comparable to the cpp and much better. its actually meant to work together, rather than pairing a silverado truck front caliper with a 90's lincoln rear caliper.
call jon on the varishocks. i know hes a dealer and he can give you some good advice.
Tim