Chairman wrote:
but the steel diff dose have a pinion mount !!
My question is will the mount on the steel diff bolt too the crossmember ? Or is the diff from the later model not interchangeable with the earlier models?
Not quite sure if you mean it has just the newer style mounting tabs, or it has the newer bracket as well? If the diff came with the newer style pinion mount & bracket just use that - should bolt up to the crossmember fine.
The brackets aren't compatible between older and newer third members, but as long as you have the right bracket to match the newer third member it will all bolt in fine.
EDIT: Added a pretty picture

