The pinion preload is set by the turning resistance to the crush sleeve. Every single differential will require a different torque on the pinion nut. I do not know the pinion ft lbs resistance number to be able to offer you a starting point.
There is a reason I do not rebuild my differentials, I don't have the proper tooling to set them up and do not know the specs. I have a local rear end shop build all of mine.
Randy - RPM