1) Use the rules from any edition of Deadlands, or any other RPG you are familiar with that includes rules that would cover a 19th Century/Wild West era. Games with relatively high PC mortality rates are probably the better choice in a tie breaker.
2) Ignore any rules that have anything to do with magic or the supernatural when creating characters.
3) Think of a plot that would work for a Shadowrun adventure, ideally one where magic isn't completely central to the plot. Look here for ideas if you want.
4) Perform Plot Conversion:
- Any journey in a car, truck, or other ground vehicle of under 100 miles is made by horse over a distance that is 1/10th as far.
- Any journey by plane or helicopter becomes a journey by train of 1/10th that distance.
- Any international air travel becomes a boat trip that takes 10x as many days to sail as it would take hours to fly.
- Any reference to Elves, Indians, or Metahumans becomes a reference to Native Americans, Chinese immigrants, freed slaves, etc.
- Sprawl residents become frontiersmen, slaves, prostitutes, etc.
- Any data, blueprints, plans, etc., become account books, ledgers, contracts, papers, etc.
- MacGuffin's become a more efficient steam engine, repeating rifle blueprints, account and ledger books unveiling fraud, rare ore samples, priceless European art, etc.
- Super-powerful megacorporations referenced in the plot become powerful local interests that 'own the town', can get away with anything, and employ their own hired guns. Alternately they can be aristocratic European families or East Coast banking and railroad interests.
- All PCs and NPC still have guns on them at all times. People being shot in the street or a running gun battle in an office building probably draws a few curious onlookers and maybe a short article in the paper tomorrow, but little more.
- Lone Star becomes local sheriffs, Texas Rangers, U.S. Marshalls, the Pinkerton Detective Agency, etc.
- NPC Physical adepts and street samurai become martial artists, bareknuckle boxers, or gunslingers. NPC Deckers become accountants. NPC Riggers become engineers (train or mechanical). NPC mages, shamans, and intelligent magical creatures (like Dragons) become highly educated aristocrats from Europe or the East Coast.
- Cyberware becomes conventional melee weapons like knives and axes for bodyware, or journals, libraries, and specialized assistants (translators, copyists, valets) for headware.
- Communication by net or phone becomes letters, sometimes sent through messengers (who can be trusted not to read the letters because they are illiterate).
- Street gangs become claim jumpers, horse rustlers, bank robbers, etc.
- The default setting becomes a nameless county in a federal territory west of the Mississippi instead of Seattle. Travel between locations within the city becomes travel through the countryside between small towns or isolated farms.
- DocWagon contracts become pre-paid funerals.
What is this?: The intent for this game is a fairly gritty and 'real-world' Wild West game with a lot of opportunity for intrigue, violence, and general murderhobo behavior. Good choice for a sandbox game, maybe. The isolation of the Wild West and the power that money and violence brought make this setting (or at least its cinematic representation) a nice giant moral void where PCs have a lot of agency.
- Deadlands is a supernatural Wild West game; I picked it for the rule set because the names and range of options available for character creation (and task resolution) are already rooted in the 19th Century American West. There are stats and rules for revolvers, riding horses, etc. If you squint and ignore the supernatural stuff (essentially make all PCs and NPCs mundanes), you get a theme-appropriate rule set for building cowboys, bounty hunters, gunslingers, saloon girls, whiskey priests, etc.
- Shadowrun is a supernatural cyberpunk game set in the (semi-)near future. A product of the go-go 1980's, it's setting is very concerned with the out-of-control growth of corporations and the eventual Japanese conquest of the commercial world (recent versions may have revised this to make it a little less dated, but I haven't really paid close attention since version 2 of the rules). Players typically take on the role of 'shadowrunners', deniable corporate assets who take on missions like swiping data from a rival, protecting executives from assassination attempts, assassinating rival executives, tracking down defectors, sabotage, debt collection, etc., for organized crime figures or powerful multi-national corporations. The world of the future is a sort of libertarian dystopia where everyone goes around discreetly armed and armored, corporations can make their own laws, and commercial disagreements occasionally erupt into running gun battles in the streets.
- Dead Man is a 1995 film written and directed by Jim Jarmusch and starring Johnny Depp. It's been described as a 'surrealist Western'. It went over Roger Ebert's head. Go watch it and see if you're smarter than he is.
What other works convey the appropriate tone?: True Grit comes to mind- the new one with the Dude, not the old one with the Duke. Maybe the old one is fine too, I haven't seen it. O Brother Where Art Thou? could work if you're interested in more humor and less killing people and taking their stuff. Most Spaghetti Westerns and their imitators will also work in a pinch if they keep the fantastic elements to a minimum (i.e., if you're thinking of Wild Wild West or Brisco County Junior you would probably be better off playing straight up Deadlands).
Why?: I watch a lot of movies late at night.
The numbers for converting a journey from one type of travel to another are off: That isn't a question. I made the numbers up in my head. Do some Googleing and calculate better ones, or just treat them as conceptual guidelines.