All I can add is that game animals have become much, much harder to kill than a hundred years ago. At one time a .44-40 lever action was considered perfectly adequate for bear (black bear, that is). These days, one would be advised to never go to the woods with anything less than a .300 magnum.
I bought my first .45-70 around 1969 when I was still in college. At the time, a 405-grain bullet, if memory serves, was just about all that was available. If there were other loads, I never noticed them. I bought my ammunition at Mountaineer Sport Shop on High Street in Morgantown, WV, next door to the Dairy Queen and the dry cleaners. I thought the ammunition was awfully expensive.
Not many years later I actually saw some army surplus .45-70. Really old stuff.
I've never seen any need to hotrod any given cartridge, although I understand perfectly the desire and have done so myself. But I was younger then.