I need to jack up the rear of the car so that I can get under it and turn the wheels. So I have a 3 ton jack under the center support but where can I put the safety jack stands? The rockers and floor are weak and rotted. Are the a-arm pivot shaft strong enough to support the car without bending. I dont see another other place.

I put mine parallel with the car where the A arms meet the frame. Fits right down in the tops of my stands and the wheels hang free.

I put mine on the front differential crossmember just outside the LCA mout brackets.  They allow the suspension to droop and allow removal of the majority of parts in the rear of the car.

The FSM is a good source of info for this question. Check the general information section.