Part number for rear axel seals

There are two (2) different oil seals available for the 7.25 rear axle.

The first is National Seal p/n 5124 which is specified for the 63-71 7.25 rear w/9" brakes.

The second is National Seal p/n 8660S which is specified for 72-76 7.25 rear w/10" brakes.