Howdy,
What are you going to use the rifle for? If you plan to use black powder for a propellant, I'd recommend the Lyman #457193, 457191, or 457122 moulds. They are 405 grains, 292 grains, and 330 grains respectively. All are plain base and work really well in lever guns. Lee also has a hollow-base 400-grain mould that works well and is easy to use.
The 457191 is especially flat-shooting when loaded with Hodgdon's 777. The 457193 is the standard 405-grain levergun bullet that was invented way back when. I start with 40 grains of Reloder7 in my 1886 Winchester, but the books go much higher.
If you plan to make a 458 Win Mag out of your Marlin, you'll want a gas-checked bullet and a thick rubber butt-pad.
You can find a bullet sizing press on eBay. I'd recommend an old #45 press, if you can find one. The newer ones are harder to use. They all use the same dies and top-punches. I size all my .45-70 bullets to .459" and lube with Alox for smokeless loads, and Wonderlube for BP loads. For really high-speed loads, you might want to try a harder lube, but those sometimes need a heated base-plate to work. Alox is great stuff.
You'll need a copy of Lyman's Cast Bullet Handbook. It is filled with good info on all aspects of casting.
Good Luck,
Bitterroot