Was all that very confusing? It can be made very simple. There are package guns available, I think from TAYLORs. Combine a conversion cylinder with the C&B revolver. Usually a Remington repro in .44, the easiest to convert, partnered with a R&D conversion cylinder in .45 Colt. Same thing can be done with the Ruger OLD ARMY, if you are not wound up about historical 'period correct" issues.
Or you can acquire the pistol and cylinder separately.
To answer your first question, with the kit I mentioned, any .451 to .452 cast bullet will work. Cast of "wheel weights" or softer. If you don't cast, there will be outfits selling lead bullets. Load light, or buy "cowboy" loads. Want to shoot real Black? Use a BP compatible lube, like SPG, or Lyman Blackpowder Gold.
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