Some other authentic combos are .38-40 (the original .40 S&W!),.38-55, .32-20 and .32-40. Some of these are harder to come by than others. The .44-40 is also period correct and was one of the more popluar combination setups back then (for those that could afford both rifle and pistol).
If you reload, check the manuals. Several manuals and online manuals now have CAS reloading information. If you don't reload quite a few manufacturers are now loading CAS ammo. Smaller operations like Black Hills up to the larger such as Winchester both load CAS loadings. They even come in period-style boxes
As for checking your bullet speed. I've never had to chrono at a local match (I believe the regional and national matches all chrono though). Most shooters who reload download so far that they're not even in the ballpark of speed. I've seen single actions shooting at, what the shooter told me, was something like 500 fps or less! Most download for quicker followup shots. Less recoil = quicker followup. When you use .44 or.45 you don't need a whole lot of speed to knock over a plate or popper
If you go the smaller caliber route you will have to get up a little speed as you're shooting a bullet with less mass to knock over steel so more velocity is critical then.
Good luck in whatever you choose.