[Buzz]

Thanks Tom - that was a huge help and it looks like the 3.31:1 diff is a '68 - '87 Series 2 unit and may or may not have ball bearings. It looks like I will have to go with a teardown and rebuild of this one as all of the new brake parts I have are matched up for this series. Joyridin' was spot on about the calipers. Although the new calipers line up with the discs when mocked onto the series 1 diff, the longer bolts needed to mount them will not clear the case. I guess I'm going to need a dial indicator now...
The good news is that the tapered roller bearings will swap onto my stub axles so if in fact I do have the ball bearings, I can replace them.

Thanks again for all of the help!