I'll have to see if I can find it, but there was a campaign style game for the Earp vs Cowboy faction where events leading up to the famous fight played a part in the fight itself. Additional participants might have joined on their respective sides, such as Johnny Ringo, Curley Bill, etc. on the Cowboys, and the likes of Texas Jack Vermillion, Turkey Creek Johnson and others for the Earps. All participation on both sides was done on a percentage basis. Even though the percentages were higher for the actual participants than the add-ons there was still a chance that some of those wouldn't be available as well.
Plus anyone who in the lead-up had to hot foot it out of town, was in jail, nursing wounds or was dead were precluded from participating.