So I called my service guy and he looked it up.
Torque specs on 2015 , 250, Sterling non-limited slip 9.75 differential cover bolts.....33 ft pounds!
Pulled the cover, very slight wear on inside about 3/8 inch x by about an 1" long and a 1/8 inch deep groove from ring gear on cover.
Gear looks unscathed.
My guestion is what about the filings from the cover, they are fine and some in there, but do I need to rinse them out or something ?
Just wipe them off?
Anyway I got a tube of MotorCraft silicone, it says to let it put it together wet, where As RTV, has you go though stages of drying, then assembling.
Things looking good!
Thanks everyone
Joe Mannix