in a body off total restoration on a '75 roadster have these problems.  installing the half shafts (rear end)  2 problems have ocurred:  1/neither side will not completely connect - approx 1/2 inch short  at outer flange with u-joint end connected,  2.  half shaft angle to severe to allow complete rotation (u-joint ends make hard contact).  original parts used:  diff, spring, half shafts, cross memeber.  new or rebuilt parts:  trailing arms,  u-joints & rods, spring bolts/washers, etc.  original shimming used in re-installing the trailing arms.  realize this could effect problem # 1, but unable to locate any info concerning "geometry" settings which might effect problem #2.   have '75 assembly manual, as well as gm chassis repair manual. any ideas would be appreciated.
copter frank in az..

If the body is currently off the car, you will have this issue. You need the weight of the body(and engine/trans) to bring the frame down to a normal height.
If you can pile a couple hundred pounds of weight on the very back of the frame, it might help. Otherwise, you may need to wait until the body is installed to connect the half shafts.
You could also dis-connect the rear spring, install the half shafts, and then re-connect the spring. This will also be fun, if there is not enough weight on the frame to be able to jack the springs up into position to connect the bolts, without the whole frame being jacked up.

Jack up the trailing arms.