The Last Gunfighter: Imposter: Imposter

The book starts off as Frank Morgan getting jailed because of a look alike that is an outlaw. He breaks out of jail and starts looking for the lookalike outlaw. He rides into the town of Chance to resupply and to verify his identity. He is told the lookalike has been raiding towns in the area and takes the job of deputy of Chance. He gets into a confrontation with a rancher from the area and settles it in his way. The outlaw raids the town and kidnaps some women, one of which Frank is fond of. Then "The Last Gunfighter" goes to rescue the women then to settle the score with the lookalike and his followers.