Dave, Did some digging in my files to see what my fuzzy memory was grasping at.
Torsen T2R was/is supposed to be their road race oriented unit. Back around 2001 it was not available for 8.75 and from their web site map it may still be true.

Tru-trac was available for a while in a full pre-load version but no longer is. That's the version I was thinking of. The preload insured some transfer of power when one wheel was spinning.

I vaguely recall the technical issue had to do with getting the axle bearings adjusted and the spacing between the axles. IIRC E-berg had to deal with this issue and covered it in an article and others may have come up with some work arounds. One solution involved using non-adjustable bearings, but a lot of us corner carver types insist on our tappered rollers. Hence the hunt for other work arounds.