Good question, I would think 80 center, 40 rear and 60 up front. My thinking is you will want less locking and more slip. Lower center diff fluids will help keep the front end down, more control, lower front and rear will allow better turning. Just my thoughts.
Check out Woodies chart on diff oil selection in the Chassis Drivetrain section may find it helpful.I just changed diff oil in my son's Typhon and went with 100 center 50 front and rear. He seems to like it?