That"stuff" is a wire mesh. Similar to a very rough 3M scotch pad. You can
pull it out once you have lifted the sides with long nosed pliers. Once out,
you will need to soak it for a long time in a degreaser. Then your powder
coater will need to bake it out before preparing the metal. There is so much
oil baked on the inside, the media used for powder coating will not adhere.
How do I know? I had one done fore an engine I rebuilt.
Robert not "Bob" Gannon