you have the right plug.correct?

I run autolite 65( or maybe it is 85? I have to look) in all my SB engines,they have at least 3/4" reach into the cyl head. no short thred plugs.

I allways make sure the seal rings are all faceing the same way,small side down. and I change them often.

oil puddle around plug hex is not from the plugs/cyls. it is from a oil leak elswhere.IMO

you should never have that much oil coming from the combustion chambers past the plug.

clean it with brake clean,airdry,throw a hand full of baby powder around the plugs. this will show where the oil is wicking from as it travels to the plug cavity.