Re-reading these posts, it occurs to me that Charles Portis, who wrote "True Grit," is said to have been a master of the history, language, and culture of the American South during that period. It's one of the things that makes "True Grit" the classic it is. Instead of a dump truck of profanity, you get carefully used language, along with a boat load of religion and moral judgements of those about you who caused trouble...
Portis' Matty uses harsh language at times, but not profanity: "The men were all chained together like fish on a string. They were mostly white men but there were also some Indians and half-breeds and Negroes. If was awful to see but you must remember that these chained beasts were murderers and robbers and train wreckers and bigamists and counterfeiters, some of the most wicked men in the world. They had ridden the 'hoot-owl trail' and tasted the fruits of evil and now justice had caught up with them to demand payment. You must pay for everything in this world one way and another. There is nothing free except the Grace of God. You cannot earn that or deserve it." Maybe you'd disagree, but to me these sentiments are harsh (and no, I'm not a bigamist). Yet no profanity at all. None needed. (If you haven't read the book, for heaven's sake, get it and do so.)
Compare the above to E.B.'s soliloquy. Had Swearingen undertaken the same observations, any guesses as to how he'd have put it?
I suspect Portis' portrait of language is the more accurate compared to "Deadwood." Likewise, "The Virginian," (Owen Wister). The Virginian (the original "man with no name") is a model of linguistic restraint, unlike his practical joking. The baddest egg in the novel, Trampas, isn't portrayed as using much profanity, either. Vile sentiments at times, but not vile language.
My suspicion is that these novels, especially Portis', approximate American western Victorian period language better than "Deadwood."