I know that from 1983 to at least 1989 the clutch packs had square tabs on them and the Differential Case had square slots from 1983 to at least 1995.
The square slots Differential Cases take the rounded tabs OK and came out with them near the end of their run.
The 2001 Differential Case has drilled holes through the case to accept rounded tabs on clutch packs but no slots for square tabs.

Is one type of case stronger then the other?
Why the change, cheaper to make?
If a case breaks, where does it break, at square slots or drilled holes?

I have both types and want to know the one to use.