Most of what I said on the Ruger Gunsmithing sub-forum goes for the Colt Single Action also. Its easily taken apart for work amd parts replacement.
One note about Colts:
It is a popular thing to mill out the top strap and fit a Smith & Wesson rear sight, on both Colts and Ruger Vaqueros. My .357 Single Army was set up in this way.
Several years ago I was shooting at the local range when my groups suddenly began to rise. Shots were soon over a foot high at twenty-five yards. Puzzled, I tried to load five more, only to find the cylinder difficult to rotate. Examining the gun, the barrel was sloped downward at a noticible angle, enough that the rear of the cylinder was binding on the topstrap. I though I had reduced this gun to a parts gun, but took it to Bob Mason, Memphis gunsmith, who was able to realign the frame for me.
As a result of this, I no longer recommend such sight installations. These loads were my normal .357 Magnum handloads, not heavy nor heavy bullet handloads, using the 140gr. Speer JHP bullet.
They had to gut that much metal out of the top strap to get the sight installed?? Man that would ruin a good fire arm in a hurry. I would never have that done. Thanks for the warning.
I don't know how much metal is removed, but the groove in the topstrap is milled out so that the rear sight tang fits flush. Also some metal is removed for the sight base and elevation stud.
This was a popular installation years ago and publicized by Elmer Keith. Its becoming popular once again for the Ruger Vaquero. My experience may have been unique, but it did happen to me.