200yrd or more MPBR is a lot to ask out of a 45-70, especially out of factory ammo that's conservatively loaded in deference to old trapdoors still kicking around.
If you're shooting a Marlin 1895, not an 1895GS (i.e. you have 4" more barrel than I have), then you'll have an advantage, but most of the 'downloaded' factory ammo will NOT give you 200yrd MPBR.
The Hornady Leverevolution 325grn FTX, for example, if you can get 2000fps at the muzzle, will be 4" high at 100yrds, then 4" low at 200yrds with a 175yrd zero.
My wife zeroes her 1895 GS at 100yrds, and has 30" of drop by 250yrds, but the short barrel only trucks 1790fps.
Even with my handloads and the 325grn Hornady FTX pushing 2200fps (dang hot out of the Guide Gun), I'd have to zero at 175yrds, then be 3 1/4" up and down from zero to 200.