If you're interested, send me a PM with your email address and I'll send you my spreadsheet of .45-70 loads. Over 200 factory laods for vullets of different types (with pointers to original data sources), plus 19 or so loads I've worked up, everything form 300g Oregon Trail LaserCast @ 1167fps to jacketed to 460g hardcast @ 1812fps.
I shoot 350g North Fork for hunting purposes but if starting over would try 350g Swift A-Frames, which were not available when I developed the North Fork loads. I also would look at:
300g Nosler Partitions (have never tired them but reports are excellent)
300g Speer Uni-Cor (I shoot a lot of these and they hold together well)
300g Barnes TSX (have never tried them but they are a TSX, which I shoot a lot of)
350g Speer FP (requires special attention during handloading to maintain COL that will cycle, but works well)
Of course, with a .45-70 you're startuing out with a big hole. A 420g hardcast running decent speeds will put a big hurt on whatever it hits. A 460g Cast Performance WFNGC running 1812fps will destroy 9 water-filled “Family Size” Minute Maid Orange Juice jugs, blow a hole in the 3/8” plywood under the lead jug and break the crossmember of the synthetic sawhorse that is supporting the plywood. Recoil is a bit ferocious (about 48 foot pounds), which is one reason I run 350g jacketed (about 35 foot-pounds, just 2-3 more than my .300 Win Mag).
My spreadsheets include chrono and target data acquired during load development and some from after. I also have a spreadsheet from some water jug bullet testing, various .45-70 bullets.