My car arrived today..and theres a moderate bit of oil (stains) on the base of the box, like the diff has been leaking. Is this normal?

Any run in tips? Do you need to use the drive spacers?

yea that is normal when they sit for awhile they leak a little space the diffs so they turn free without any fluid then fill them and go

The oil is from sitting in the box for a while. We suggest to re-space your diffs like chip daddy has suggested and refill them and then break the Matrix in.