As I’m working on a 3D model of a freight car, there are some parts that lend themselves to reuse. Brakes, stake pockets and pipe fittings are natural candidates for standardization. So, I’ve established an OnShape document of some standard parts that I can import and use on any other car I might design.
John H. White, Train Shed Cyclopedia, and reprints contemporary works on railway equipment provide many of these details. Indeed, while drawing the triple valve attached to this air reservoir, I came dangerously close to understanding how the real one works. Sadly, most of these resources don’t have dimensions; so I’m going to have to get myself up to Squamish, where there is at least one car with KC brakes, before I can finalize the design. However, the version shown here should stand in on the coal cars, at least for now.
Pembroke:87 
Not a KC type but similar. Hope that helps.