Does the rear end need to be broken in?

OK. Just for future reference for anyone curious, or anyone else down the road... I did talk with Dr. Differential.
He just just to use "Conventional Gear Oil". I guess whatever works? He did say to stay away from Lucas though. I guess it bubbles to much. He also said to use the Sure Grip additive in BOTH cone, and clutch type! He said... if it states, "Posi, or Sure grip" the additive will work.
Something else that was mentioned that was even if the the Gear Oil states that it has the additive already in the gear oil, add some more, because what they add isn't enough.

I know nothing obviously, I'm just passing on what I was told.

Thanks Everyone!