wsg,
After shooting a friend's Marlin 1894 Cowboy, I decided I simply had to have an 1895 Cowboy!
My first choice would be a Marble's medium-range tang sight like Tom Horn had on his Winchester M1876 .45-60.
I am even considering a long-range vernier tang sight so that 26" barrel can REALLY reach out! The basic M1895 with Ballard rifling is plenty accurate out to medium-long distances, and this new Cowboy with 26" octagon barrel should be even better!
John