Just remember, each book is going to be different. A lot of them play it on the safe side of the loading spectrum. Also they give you load data for there specific bullet as well. As where powder makers like Hodgdon will have higher charge weights.
I buy several reloading manuals and I don't hot rod my 45-70 to much. I am in the 1900 fps range with a 405 gr. bullet, using H 322, which by the way is also a great powder for the 45-70, as is IMR 4198 and H 4198.
I also compiled a lot of load data from other people, as to what they shoot in there specific gun, and if it falls within safe reloading practice, I give them a try for accuracy. The cool thing about the 45-70, even the lighter loads will kill anything walking in North America.