I would not hesitate to remove the center stud (for the spin on) and stone it back to flat. within reason of course. if there are really deep pits then clean well and epoxy. a lot of racer guys use epoxy to profile intake ports you know. in the event anything broke loose, it has no where to go.... certainly nothing is going into the engine against oil pressure
I can also think of more elaborate things to do, like making a pilot to put in place of the spin-on stud and using that as a guide for a disc with sand paper. like a spinning surface plate.... solid, with very little slack. I would not even consider welding it.... there is a lot of material there to work with. note that with the stud out, everything is the same surface.... thats how it was milled.
and no, that damage is not from a gasket incident. looks to me like the PO had trouble getting the filter off... guessing he stabbed it with a screwdriver & tore the can and then used a chisel and other harsh tools to a stupid thing
if I'm answering your question I assume the basic points have been addressed, such as: did you do a compression test? is it still on fire?
Last edited by Beezerboy; 02-03-2019 at 07:59 PM.