The current Hodgdon H335, H322. Alliant Re-7, H4198, and IMR4198 as well as Varget and IMR4895 have a full gamut of loads available to be utilized in the 45-70 without even considering the 45-90 which was a Winchester Express chambering of the 45-70. Light bullets with high for black powder velocities. If talking points are needed at the range, a 45-90 might be nice, but I've never run out of load options in 35yrs of the 45-70 in Ruger and 1879 Rolling Block loadings. I've seen serious shooters flinch wildly with my Ruger loads. A 6pound #3 with 300gr at 2375 fps is serious shooting. With 405gr running at 2200fps, it'll definitely waken you up. These are out of a 22" barrel and 1/2"groups are possible for 3shots from 1550 to the 2375 load. I feel you'll be lucky to achieve that with a 45-90, unless you go to a longer barrel. The loading density will be less, for sure. The 45-70 is one inherently accurate old round.