While I think the Ang Lee Brokeback Mountain Movie is a very good movie in the "stand-alone" sense, I actually prefer Annie Proulx's original story (I refer to that as "the book").
I chose "L. D. Newsome" as one of my options here because while Lureen's father-in-law is talked about in the short story, he has no name in it. Lureen doesn't even have a last name in the book." Annie Proulx NEVER had Jack Twist work for his father-in-law's farm and equipment company. Jack worked for the company and had a vague managerial title and was a buyer after Lureen inherited it. Jack would not have enjoyed working for a man who hated his guts and according to Jack in 1967, he and Lureen were getting no financial help from her father at all.
K. E. Del Mar more than likely had a problem with his own sexuality and might have suffered from his father's hatred of queers, too, just like Ennis did. When Ennis and Jack were up on Brokeback Mountain, Ennis said that his brother lived in Signal and his married sister lived in Casper. Notice that the book did not say K. E. was married.
Cassie Cartwright - She was created for the movie because when the last time that Jack and Ennis were together, Ennis said "he'd been putting the blocks to a woman who worked part-time at the Wolf Ears bar in Signal where he was working now for Stoutamire's cow and calf outfit, but it wasn't going anywhere and she had some problems he didn't want." Signal and the Stoutamire ranch were not even in the same county as Riverton, Wyoming and the book says so. One "putts the blocks to" a vehicle to see its underside or the main-frame which is a "chassis" (pronounced "chassie". The screenplay writers used a play on words in that situation. I personally think that Ennis made the woman up to tell Jack, "I am a man; I'm still not no queer."
Jimbo, the Rodeo Clown, doesn't exist in the original story either. The guy who is the bull fighter clown in the movie when Jack is supposed to be riding a bull is not even built the same as the actor. The Alberta Rockies Gay Rodeo Association (ARGRA) assisted in the production of the movie's rodeo scenes.
Speaking of Rodeos and bull riders, Ty Murray, the president of the Professional Bull Riders Association (aka PBR), stated on a morning talk show on a major TV network that he like the movie. Bernie Taupin, the writer of the lyrics of "A Love That Will Never Grow Old," is one of the stock providers for PBR rodeos in the west. Taupin is one of Elton John's song writers.