As far as I can see, there are basically 5 Audi components involved in the rear anti-roll bar setup for the V8. (not counting nuts/bolts, etc)

Different cross member-
441505099A- no ARB
441505099F- with ARB

ARB- 4A0511409B
ARB drop link- 4A0505389
Rubber bearing- 4A0511327
Clamp- 855411335A

The 'drawings' on etka imply a different rear wheel bearing carrier, but I didn't see anything to show different part numbers.
The orientation of the camber arm inner connection may be different.

Has anyone succesfully retrofitted a rear ARB? Or even an alternative supply?

Any comparison photos available or known about?

85 WR quattro
90 V8 Silver, 91 V8 Black, 93 V8 Lago
93 100e quattro V6. Titan, i think