Wow. So you've decided that no one anywhere ever ran a wild west game without changing rules? That's either the height of hubris or now your just pulling our legs that you really believe that. I might tweak the firearms a little bit because they should be slightly less effective than the modern equivalent but otherwise I don't see why I'd change a single thing.Don't be silly. No D&D based wild west game will keep the rules, character stats and class abilities exactly the same as in the PHB. Of course there will be changes.
Well, that and add gatling guns for my ogres. Because I want to replicate super mutants from Fallout.