I believe the color code for brilliant silver is 744 . You should be able to double check this by looking at the metal plate that is fastened to the chassis abouts where the hood ornament ought to be (while you have the hood open, obviously) On that plate a various 3 digit numbers which correpond to option codes, etc. 744 ought to be among the bunch of them.
As for your oil filter...I haven't the foggiest idea. How about the PartsShop?
Have Fun!

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'83 300D-T