you're running blocks and stock springs? how they flex?
and your missing a nut on your passeneger side u-bolt.

  LOL good eye....

Actually if you want to have an ideal setup that wont haveto mess with much take into concideration saging (since im sure lots of people have run these shocks you should be able to get a pretty good Ideal of where they will settle too.) then flex out your rear suspension to the max and measure the distance from axle mounting surface to crossmember surface on both sides of the axle.  This should give you a shortest and a longest measurement.  Then when you get your shocks you should have a real good idea of how you have to place them to keep from bottoming them out/ or having them limit travel.