First, lets get you some brass at a decent price.
www.starlinebrass.com 250 cases for $102.
Next, lets get you some bullets at a decent price.
www.midwayusa.com 500 bullets for $119.
I would also purchase a copy of Lyman Reloading Manual 49th Ediion.
The 45-70 has a large loading range, from Trapdoor through Marlin. According to Lyman Reloading Manual 49th Ed, the load you selected is only 1 grain under maximum and it is NEVER a good idea to start with a maximum load. The good news is that different manuals use different pressure ranges for Marlin loads and Lyman is on the low side of the various manufacturers. I have NEVER had a bad load from Lyman and I trust them. But beware, some powders are temperature sensative and a load which is perfectly safe in winter may stick in the chamber in summer. This is another good reason to stay well under maximum, particularly if your gun is most accurate with a somewhat reduced powder charge. The only way to know how your gun will react is to test for accuracy and signs of pressure, working up starting low.
I actually started in the Trapdoor range and worked up 1.0 grain at a time, all the way to maximum Marlin load, per Lyman manual. I loaded 5 rounds each at the 1.0 grain increment. Each load was then test fired to an individual target and marked according to the load. As successive groups are fired, a pattern of group size emerges on successive targets. When finished, you should find an area where accuracy starts looking really good, lets say for arguments sake between 48 and 50 grains. You can then load 5 loads each at 0.5 grain increments and retest. For example, 48.0 then 48.5, then 49.0 then 49.5, then 50.0 This way you can zero in on the load with greatest accuracy. When you are testing, check primers for signs of excessive pressure and difficult extraction and stop the test if you do see signs of excessive pressure. All firing should be done on a calm day from a benchrest. I do my 45-70 accuracy testing at 75 yards, due to use of iron sights. For my hunting load, I am looking for the load with the smallest group size at a reasonable high velocity. If I dont find it with one powder, then I try another. I have found IMR3031 to be really excellent wtih Marlin loads. IMR4198 seems better with cast bullets or jacketed at Trapdoor velocities.
Wtih my Encore, I found 2 points of really excellent accuracy with the 300 grain Remington JHP, the first at the high end of Trapdoor range and the other near the top of Marlin range. The low point was with IMR4198 and the high point was with IMR3031. The Trapdoor load is a really pleasant load to shoot. The high end Marlin load is not as accurate and is a bit stiff on the shoulder. I find that high end Trapdoor loads are a loat more fun to shoot and hit the 100 yard gong with AUTHORITY!
If you extensively shoot high end 405 grain Remingtons at high end Marlin velocities, your shoulder may be sensitive for a day or two. Even at Trapdoor velocities, I think that this bullet should kill any deer that ever walked this earth, like hit by a bolt of lightning.