Best I remember the difference is that the HD version of the dana 60 has more material ( webbing) around the carrier part of the housing. It will also have HD60 cast into the housing around the carrier.
This is correct, internals the same. Got one from a ford wrecker a few decades ago. Still got it under a 50s Mopar.
Had the same spline as the 8 3/4s. Came with the track lock rather than the power lock.
