As a huge Ballard fan for the last 45 years I'm tickled to see another fine old Ballard rifle. Even if it turns out to be one of the cast actions the .25-20SS is still a great cartridge, just needs mild loads if it is cast. I can't give you any help with what rings fit until you have it, and can post what type of rail it has, and how scope rings might attach?
It really does have that "rook rifle" look to the build, and certainly whoever put it together had that in mind. A nice old Lyman or Fecker scope in the small game style would look appropriate for a rook style build. I have a Lyman 438 on my Ballard 3f Fine Gallery in .22LR.

[Linked Image from i.imgur.com]