Magnum Research also puts out a revolver in 45-70 as well.
I have the .45-70 BFR with the 10" barrel. It will shoot 300 to 500 grain bullets. Very comfortable and accurate. The gunsmith at Magnum Research says to hold the max pressures to under 31,000 PSI. That makes it stronger than a typical trapdoor at around 24,000 CUP and not as strong as the Marlin 1895G lever action at 40,000 CUP. The falling block Ruger #1 rifles can sustain 50,000 CUP. Magnum Research just announced availability of "the other cylinder" for the BFR in .45-70. You can get the 450 Marlin cylinder for your .45-70 BFR. You have to send the revolver back to the factory to have the 450 Marlin cylinder fitted. That gives you the ability to fire either .45-70 Govt or 450 Marlin from the same revolver frame by just swapping cylinders. The cost for the other cylinder is $150. The 450 Marlin brass is belted at the case head so you don't accidentally stuff it into a .45-70 rifle or revolver that can't handle the higher pressures.
I reload all my own ammo in .45-70. I build the cartridges with around 29,000 CUP as a target pressure so they can go in either the Marlin 1895G or BFR .45-70. The brass case is so big that you have to add a small cotton batting wad on top of the powder to keep it near the primer. That is especially true with the small 300 gr bullets. The 405 and 500 consume enough case volume to keep the powder back where it belongs.