If you have an original 1894 Octogon model from 1973, I'd hesitate to alter it. There were only 2,957 of them made which makes it somewhat rare.
You could probably sell the rifle as is and get a new 1894 Cowboy, still octogon, with ballard rifling, for very little cash outlay, certainly less than it would cost to rebarrel and existing rifle. Some collector would probably love to have it. I have one, shoots jacketed bullets well.