RE: Looking for CENTER DIFF! Please help...
Most ofna diffs are around the $80 mark new, but I highly doubt you will see one on ebay complete.
OFNA diffs are tough as nails, I doubt you'll be able to damage the bevels in the center. Maybe in front or rear but not the center.
Have no fear, OFNA does drivetrains very well indeed, the Mutilator center will hold up comfortably to 6S 2200kv.
Pro tip, put 50-100k oil in it.