I bought a Pietta, 1860 army sheriff's model (not ever produced by Colt in the following configuration) with the 5 1/2" barrel and fluted cylinder.
I don't shoot BP for my CAS however it is a nice little pistol using paper cartridges. I read about the Kirst Conversion for the 1860, was intrigued and ordered one.
I have to say I am impressed to say the least. The installation required relieving the right recoil shield of some metal to allow the loading of cartridges (.45 Colt) into the cylinder. The conversion kit is very similar to the Richard Mason conversion except the back plate is not permanently attached to the recoil shield. The kit comes with a replacement (and well made) two step hand. The top of the hand will time the original 6 chambered cylinder, while the lower step will time the 5 shot conversion cylinder. This system allows me to switch back and forth between cartridges and cap and ball.
It is a bit pricey at $366.00 which is more than I paid for the pistol, however it is unique and the smithing I did with the follow up bluing of the recoil shield yielded a nice looking pistol, I can use cartridges for CAS. It would have been cheaper to buy a Richard Mason Uberti from Taylor and Co. however it was a rewarding experience. The conversion kit times perfectly with both cylinders and the little pistol is very accurate with .45 Colt cowboy loads.
It has become one of my favorite shooters. I am contemplating purchasing the ejector assembly next year (another $125.00) however I will probably leave it as is so I can switch back and forth between cartridges and percussion.