I would walk past a long gun in 45ACP just as I would one in 9X19. But one in 45Long Colt I would take tomorrow. Just my thoughts only but 45ACP is an anti personel round were as the 45LC is that and more. Loaded up in modern firearms they will out perform the 44mag.

Any flat nosed bullet should work fine- read better than pointed bullets- on animals.

Jim Kent at Buffalo Gunsmiths in Toowoomba would be one I would contact for work on lever actions.