So the diff held up fine through my first race on it. It certainly is better with corner exit grip, the other one had been giving up for a while it seems.
The clutches still chatter a bit every now and then, but 75% of the time are fine...so I think it's going to finish breaking in just fine.
I'm still trying to figure out a way to finagle a floater rear end with a TruTrac and a set of new brakes front and rear...but in the mean time, I'll just make do with what I've got for now.