There was a couple popular conversions to cartridges. One was the Richards/Mason, which became the 1872 Colt Model and, another was the Thuer. I have read and seen a few conversions by blacksmiths/gunsmiths but they were obviously not production conversions.

I don't know of any cylinders that were available just to buy and swap out. One must remember that there was very few cartridges in existence at the time. The 45 Colt wasn't available until after 1873. The Richards/Mason conversion was chambered for the 44 Colt and, there was rimfire conversions available. The 1851 Colts were chambered in 38 Colt.

When Jose Wales changes out the cylinder of his 1858 Remington he is replacing the fired cylinder with another percussion cylinder that was previously loaded. Hollywood has that part right as the practice has been recorded by Civil War era chronicles.

Jose Wales also carried an 1849 Baby Dragoon in a shoulder holster.

I have the Uberti version of the 1872 Colt in 44 Colt and made my cases by shortening 44 Spl. and turning a few thousandths off the rim diameter. I'm shooting a 200 gr. Lee bullet that is the same as I shoot in my Uberti Schofield in 44-40. I was pleasantly surprised at the accuracy I was able to achieve with both revolvers, the '72 Colt in particular. The Schofield would shoot better if the sights weren't garbage....even after I worked them over so I could see the blade in the notch.

A large part of the character "Jose Wales" was inspired by a man who was from only about 10 miles south of where I live and, of course Hollywood took its liberties. His name was Bill Wilson. The yankees did not kill his wife and family but they did start the feud and Wilson became a horse thief/renegade. I used to work with his great, great grandson who still owns a part of the family farm. His name is also Bill Wilson and after he retired he wrote a small book about and began reenacting his ancestor.

If you pay attention, near the last of the movie, when the last fight is over and Jose is standing there bleeding and...I can't remember the bounty hunters name but, he says, "isn't that right Mr. Wilson." An Jose answers with that droll, "reckon so."