I once had a 45-70 built on a Siamese Mauser. It was not sporterized and the only modifications were a new barrel and changing the magazine box.
It was the worst kicking gun I have ever fired but I suspect it was mainly the fault of the original stock and it’s steel butt plate.
I would love to have a Winchester 1885 or a Ruger Number 1 in 45-70. Heck I would even take a Winchester 1886 lever action. A hot loaded 45-70 would have to be effective.
You might also want to see if you can get an older (pre-remington) Marlin 45-70 lever action. Friend of mine has one and it’s a very sweet rifle.