Reading The Hangmen of Sleepy Valley, a Forgotten Friday recommendation from James Reasoner lead me to this book: Death Rides The Pecos, the first appearance of Twister Malone and Chuckaluck Thompson. Originally published in 1940, the copy I have is a 1950 paperback.
Twister and Chuckaluck knew there was somebody riding ahead of them as there had been a cloud of dusty haze all day along the trail. They never saw him, though, and when they heard the gunshot, they raced ahead to find a man shot through the heart.

In looking over the body for an identity, they found a letter from a young woman named Sally Blaine asking uncle Peter for help. Her father had been killed and the ranch was about to go under.

Reluctant at first, the two partners finally ride to the ranch to find Sally and an old Mexican couple the only ones living there. Things were in disrepair. Naturally nosy and unwilling to leave a young woman in trouble, they decide to take a hand.

Hamp Jerome, a dead-eyed gambler holds the IOU on the ranch, lost in a poker game the night the father was killed. The killer is apparently her beau, who is in jail waiting trial. There’s another young rancher willing to pay the note off. All Sally has to do is marry him.

Then a stranger rides into town wearing uncle Peter’s gear and claiming to be him. Twister and Chuckaluck know better, but don’t say anything right away.

They start poking around, seeing what they can stir up. That draws three bullets in Twister’s hide, a pile of gold coins and bills ina dice game from Jerome. There’s gunfights, cattle rustling going on, and the two partners get caught up in a mob mentality as someone starts spreading the word that they are responsible for everything.

Recommended for anyone who likes a good, old-fashioned western.