It's basically what they call a 45-90 with modern powders.  I'm not too familiar with 45-90, but basically if you're using smokeless powders its considered a 45-90 Express.

I get my CZ 550 Safari Magnum in 416 Rigby this week!

ETA: For shits and giggles, here's a 416 Rigby next to a 45-70 Govt:

I myself just bought an 1886 Short in 45-70 Miroku made one on GunBroker for  close to $1k. Don’t know if I overpaid but how does yours compare to the 1886 Short in case you have received and shot it?

In any case, I am in the works to get to a 30-30 JM Marlin and might sell the 1886 Short in a while.

OK, Rigby wins.

But for everything short of a rogue bull elephant, would the .45/70 be an acceptable choice?

ETA - at relatively short range, of course.

Welcome to the Miroku family!  Very nice rifle, I used to own an 1886 Short!  If you got it for around $1,000 then you didn't overpay at all.  Typically they seem to go for close to $1,100.  I ended up selling my 1886 Short with the intent to get the 1886 Deluxe eventually.  In terms of function and overall quality, the Short and the Deluxe are complete equals.  The cost difference between the two is mainly due to the cosmetics.  The Deluxe has the case hardened receiver, grade IV walnut, heavy octagon barrel, and pistol grip stock vs. the Short having a blued receiver, regular walnut, round barrel, and straight grip stock.  Again, pretty much all cosmetics.  Functionally they're going to be the exact same.

45-70 is a hammer up close, but Idk that it has the penetration for the really, really large game animals like an elephant, rhino, hippo, etc.   A 375 H&H is even considered a bit on the small side for those animals (although with a good bullet it can take any of them), and that round is no slouch.  From what I've read anything .40 caliber and above (in regards to "safari rounds") should have no issue taking anything on Earth.  The only round in that group that may not be up to it is the 450/400 Nitro Express.

I think the 45-70 is best served as a defensive weapon for bear and moose.  If I was hiking or w/e in grizzly country, I'd take the 45-70 with Garret rounds over the Rigby.  The Rigby has way more power, but as funny as it sounds it's really overkill for anything in North America, even the largest bears.  Plus you can get faster follow-up shots off with the 45-70 lever action, and to add to that any defensive situations where you'd need would probably be well within the range of it's capability.  Now if I was actually hunting a bear or moose, I'd take the Rigby because you get all the power with the ability to take much longer shots than you could with the 45-70.