scully, ideally, the centerline of the shock should be at a right (90 degree) angle to the control arm at full bump as viewed from the rear of the truck. That will insure increasing spring rate as the control arm goes into bump. What you have now is a decreasing spring rate arrangement (not good). It looks to me like you're gonna have to cut the frame out and rebuild it to make room for the top shock mounts if you want to continue using the bottom mounts as they are.

Like Mike, I'm also wondering about the rate of the springs you're using. I'd start with something in the range of 150-170 pounds per inch on each side (2 springs on each side at 75-85 lbs each). If you get it sprung too heavily, that light truck rear end is gonna be real skiddish on bumps.