I found that oil filter article in my searches, but didn't see my oil filter included in it.
Took a few more pics.
Block casting code -- 3769925
Block casting code -- 3836850
Engine serial number -- ??
Not sure if it means it's stolen, but it doesn't look to me like there ever was a number there. The machining marks look consistant across the face of that ledge. Know of any other places to check?
Regardless, I'm feeling confident enough to order a remote mount base. Bye-bye nasty oil leak.
Ben