"Aces and Eights" is "pure" wild west, as opposed to Deadlands' "weird west" (which is probably my second favorite setting in all of rpg-dom mind you).
There are also the "general" systems out there with versions/supplements for that (GURPs, I'm sure there's a PbtA, I know there's a "Forged in the Dark" cover, Genesys could do it easily and well).
Both Shotguns n' Saddles and Devil's Crossroad have a supplement to add supernatural elements to both of those games. And both are available for cheap on DTRPG.
There is a Wild West version of Werewolf: The Apocalypse
Cypher System can be used for wild west; The Strange in particular makes sense of that by having pocket universes with rules particular to certain concepts.
I'm thinking of running a one on one game set in the wild/weird west. I'm going to be useing deadlands/Savage worlds system if anyone is interested let me know and fyi I'm thinking this will be adult oriented. Hope to hear from someone soon.