I was real glad to see someone make the point of taking care of the cylinder endshake before barrel fitting. Not doing so is kinda like building a house without making sure the foundation is square & level. It's also a good time to check yoke alignment & play before trying to fit a barrel. Another issue is to make sure the faces of the cylinder are parallel and at right angles to the axis of the cylinder. I once worked on a gun with a cylinder with a 0.007" out of parallel situation-the factory fixed that part free before the lifetime warranty. Surface grinders are wonderful things

Once the cylinder is where it's supposed to be, you can measure from the front of the frame to the cylinder to determine the correct length of the barrel tenon to allow the proper B/C gap. This can be set on the lathe at the same time the forcing cone is corrected/cut.

There is a method of torquing fasteners (and barrels) where the number of degrees of rotation after contact determine the torque. Based upon observation, I believe this is the system S&W uses on one piece barrels.