Just purchased a Pietta 1858, the timing was off, and the cylinder and barrel don't line up. This is what I have done to rectify the problem, let me know if I have gone in the right direction. Since I have the availability of a machine shop, I reproduced a longer hand to bring the cylinder in line with the barrel. I then filed the cylinder stop window to line up with the edge of the cylinder stop notch. I had to designed a new offset cylinder stop to compensate for bringing in the cylinder closer to the center of the frame. The newly manufactured parts were then filed for proper fit and timing, the parts were then case hardened and re-installed. Action is now smooth and tight, the cylinder has no play in it.
I still haven't shot the revolver, but maybe within a couple of weeks, I'll have the time.