You might want to consider a rear hoop setup similar to this:
Or something similar to this:
If at all possible tie the two loops together or triangulate them to something inboard.
Here are the same hoops in the pic above, but with the bracing installed.
The idea is to tie the forces that the shocks will put into the hoops and direct them towards each other.
I also agree w/bdkw1. *Rotate those mounting tabs (which are fine if they're 1/8") around the tube 90 degrees inwards. *Just make sure you can still get the bolt in and out. *Tends to make you swear when realize you can't get the bolt into the hole.
Locate your upper mount by compressing the shocks fully (full bump) and leaving at minimum 2" of ground clearance under the rear end of the car (with the wheels on the suspension. *I'd go 3".
Once you find more or less where the full bump upper shock mounting point is extend the shocks fully (charge them to about 75 psi w/air) and see what you end up with for axle/cv angles at full extension.
Hopefully full extension won't put the cvs past working angle. *If it is, drop the chassis to the point where they don't bind. *Measure how far you had to compress the shock to keep the cv from binding and get someone to make you a spacer for the inside of your rear shocks.
You might also be able to move the location of the mount around and find a spot that works. *There will be a small window of location for the upper mount that will hopefully work. *It may be hard to find, so don't get frustrated.