On either side of the leaf spring. Was told that there should be a piece about as think as an inner tube on both sides of the rear leaf spring to eliminate some of the noise from the axle.
There is a rubber insulator that goes on top and bottom of each rear spring on the 52 and 53.it is 2 5/16" wide. I goes between the steel insulator and the leaf spring. I wish I knew how to operate this computer so I could send you a picture from the Ford ch***is catalog that I have. But I see if I can get some help.
The rubber insulators on the rear springs for my car were in terrible shape. I eliminated them and did not notice a difference in noise or vibration.