The front sight is easy enough to change on any revolver, just remove the one you don't like and dovetail a suitable replacement in place. On the Colt style open frame revolvers, the rear sight is tradionally on the hammer for the C&B types and either on the cylinder ring (Richards) or the breech end of the barrel (Open Tops and Richards and Mason types) Either of the conversion style rear sights are more rigididly fixed than the hammer mounted rear sight but good accuracy can be obtained with all of them. I happened upon the Richards conversion and like the rear sight position. The ring is fixed in place so the sight does not move. The sights on the later style conversion, being on the barrel, also do not move about so not much difference there. As for sight radius, it is hard to find a Richards conversion so you have the shorter RM of Open Top to choose from. Both are very good choices. Avoid the 45 caliber chamberings as they have a history of cracking the forcing cones.