Sharps1874,
It would take a book to cover everything you want to know real well, but here goes with some info.
The smokeless powders you have will work well. Especially the 3031 and 4198. I used quite a bit of both.
A good bullet would be the Lyman 457125. A lot of people think there are better, but it will more than do to start. It sounds like you want to buy your bullets so I imagine just about any commercial caster will have this bullet.
The best black powder would be Swiss in either 1, 1 1/2, or 2F. It's also the most expensive.
A good handbook to get for loading black would be Steve Garbe's and Mike Venterino's "Reloading Primer".
If you're not aquainted with Buffalo Arms Co. check out their web site at:
(You need to Login or Register to view media files and links); It's a candy store for black powder shooters and will have the book mentioned above, plus everything else you can imagine you'll need.
Shiloh was right in suggesting you not load for the gun till you get it. Altho bore dim.'s for the .45/70 are pretty well standardized in modern guns, slight variations can be found. You'll want to slug the bore so that you can size, or have sized, your bullets from .001" to .0015" over groove diam., and of course set your seating dies for proper OAL in your chamber. You'll have to experiment with the OAL as some have found their guns work best with the bullet tight into the rifling, and others like it a few thousandths off.
Loading a black powder cartridge is pretty simple. Once you've decided what your OAL is with at least a .030" wad of some kind under it, all you need to do is fill the rest of the case so the powder just touches the wad. This will be zero compression. After that you just keep adding a gr. or two of the powder you want to try out until you reach the best accuracy. You will need a compression die (available from BA) to get the necessary compression as you increase the load. You don't want to compress the charge with the bullet.
What's listed above is a very general way of working with the .45/70, and like any other caliber there are all kinds of tricks you can do to get the most out of it. Garbe & Venterino's book will give you everything you need to know, even if it's becoming a little dated, it will get you started in good fashion.
If you've got any specific question don't hesitate to ask as there are a lot of people on here that can help you out.
PETE