My dad was born in 1904. He swore. He blasphemed, to be more exact - took the name of the Lord in vain, swore by Jesus Christ, Hell and damnation, damned people to hell.
He used 'son of a b*tch', sometime abbreviated to 'ess oh bee', 'b*stard', and 'bloody' (sometimes 'bloody-*ss'), and 'Christly' - these were often strung together in various combinations. He even used 'son of a sea-cook' (he'd been a cabin-boy in his early years, so I believe this may have had some particular relevance), an epithet I've otherwise only seen in books.
What he did NOT use were the sexual swear words that I learned in the schoolyard and from reading graffiti. He told me that those were 'baby words' for children who didn't know the real words for the body parts and activities. I haven't watched Deadwood, but I've heard they mostly swear with what my dad called baby words.
I'm pretty sure he would never have used any variant of mo-fo, because in the milieu where he grew up, I think if someone said that to you, you pretty much had to kill them, or at least beat them into insensibility. That's the impression I have.
-Barbara