I have done quite a few street and strip diff's and this is the procedure I use on GM diff's.
Take the wheels off and make sure there is no drag on the brake shoes/ drums.
Before starting and using an inch/ pound torque wrench turn the pinion nut and see what the rolling torque is.
After the seal is replaced as you tighten the pinion nut after all the slack is out of the bearings keep checking the torque until it is the same rolling torque as old setting. I have made tools to hold the yoke as I turn the nut, plus a tool to remove the yoke.
