Bis,
I own and shoot 7 different .45-70 single shot rifles. Several original Ballards, a Hepburn, Ruger #1, and a couple of very old Marlin lever actions. I shoot cast in all of them, and use a number of different loads, depending on what I'm doing with a particular gun.
I use an old Ideal mold that casts a 420 gr. bullet which seems to work well in all of them. I also have one of the inexpensive Lee tumble lube design bullet molds that casts a 360 gr. bullet, which is lubed with Lee Liquid Alox. Surprisingly, this has given some of my best groups to date.
When buying bullets, I have purchased some Meister brand hard cast bullets from Midway, and although they are pretty reasonably priced, they give good accuracy, and make decent hunting rounds, with little or no leading when pushed up to 1500-1600 fps. I took my deer last year with a 1870's Ballard #4 in .45-70, using the Meister bullets, and expansion was adequate, even on a small boned animal like deer. I think it would hold together well, even on elk, if used for them.