If you can get to Big Timber Montana you could probably pick up an 1874 Sharps over the counter from C-Sharts or Shiloh. They are not far from each other and the 45-70 is more available than the other calibers. Plus more reloading data is available for the 45-70 and you can shoot either smokless or black powders. I have seen some loads in smokless for the longer cases but the 45-70 is capable of anything that they can do at a much cheaper price.
Some of the Itialian Sharps are made very good so if money becomes a problem then you have another avenue. I myself prefer the American made but I do own a Pedredi Sharps that shoots very well. Not sure but Pedredi is part of Pedersoli and I am not sure if I have spelled the name correctly. My 1874 has a very sweet double set trigger.
If you think the rifles are expensive wait until you start purchasing creedmore sights and replace the front sight with a globe level sight.