If you like 45-70 performance but are not stuck on the cartridge, you can rebarrel any common magnum rifle for the 450 Marlin, which is approximately a 45-70 with a belt instead of a rim. Then you don't have the problems of feeding a rimmed case.
Bruce
+1
I have a Simese action I had rebarreled to 45-70 and have many problems
1 Stock, So far I could only find Fajen that will make it and it has taken me about 6 years to finally get a stock out of them. (great looking stock bby the way - Black walnut - lindseed oil finish. (needs about four more coats but I am waiting for it to completely dry before scuffing.)
2 feeding ammo - the feed ramp was designed for a 8mm tapered bullet (think 303 brit)
3 adjusting the feed ramp to feed the flat pointed factory ammo. (the Hornady Pointed flex tip helps) but lots of sanding and filing.
The 450 Marlin was introduced a year after I started the project. I thought about the 458X2 but wanted a factory round. And did not want the head aches of 458 Win Mag.
Had I known about the 450 comming out the next year, I would have done it.
Easier to get a 98 action.
easy and multiple stock options for the action.
Bolts are already turned down.
and parts are availible to change the safety from the over the top wing to three position M70 types or the slide like the Remington 700.
Having done it. and wanting to do it again I would look to use a 98 action and make it a 450 marlin.