XA Falcon Rear End

I have a 1972 XA Falcon. Rear end appears to have movement - diff moves to the left and sags on the right side mostly. Have put in second hand leaf springs but stil lthe same. Any ideas??

don't know what you mean by moves to the left and sags. All those cars ended sagging in the back one way or another, but the diff moving to the left... You mean like it's offset, not centre.