Hornady make the Leverution ammo, but I think that's only if you use a lever-action. I think that all 45/70 Govs are either lever, or they're break actions.
You can use them in any rifle though they were designed to be able to let you shoot a pointed bullet in a tubular magazine. I don't use the 45/70 but I shoot a .450 Marlin which is basiclly the same thing just loaded hotter for hogs. I either shoot the Hornady 350 grain regular bullets or the new Levervolution bullets and but shoot great.