[jonzcustomshop]

60-62 have the drop out center, like a ford 9 inch.
the trailing arm pads are welded on wider than the 63-66 (not sure the actual measurement, but for example if the trailing arm pads are 50 inches center to center on the 60-62, they are about 47 inches center to center on a 63-66), also the center link is located in a different spot on the rear.