Over the weekend I shot a few 45-70 rounds a friend loaded with jacketed bullets, the first I've shot in mine. His loads were 405 gr. Remington JFP bullets, IMR-4759 powder (not sure how much), cci LR primers, and starline brass. They had about twice the kick of my puny TB loads, but were probably only traveling about 1500 fps (vs 900 for mine). 4759 seemed to burn completely, as does the TrailBoss I prefer. While I like IRM 4198 powder a lot in 222 loads, I'm not interested in full power powders for my 45-70. That said, my best advice is to follow the suggestions of the Hodgdon/IMR folks at their website:
Cartridge Loads - Hodgdon Reloading Data Center - data.hodgdon.com
While I haven't tried them, these two from their "Trapdoor" loads look good to me.
300 GR. SIE HP Hodgdon H322 54.0 1850 18,100 CUP
300 GR. SIE HP IMR IMR 4198 45.0 2008 23,500 CUP