you have a great gun and in a great caliber! a nice straight walled cartridge like the 45-70 is a great candidate for reloading, especially in the marlin which can be loaded to a higher level then what is generally commercially availible. I have a marlin lever in .444 marlin and a handi rifle in 45-70 they are well suited for medium to close range hunting of all game in the lower 48.
I've got a Marlin 1895M .450 Marlin which is very similar to yours. I love it!! I consider it a little overkill for deer hunting, but bought the gun to hopefully one day fulfill my dream of hunting Grizzley.
Proud owner of a Guide Gun for about 10 years. Winchester factory 300 gr HP's work fine for thin skinned game. My hand loaded/personally cast 340 gr flat point at 2100 fps is a beast. Large (300+ lbs) feral hogs drop in their tracks.