Luke
I am not an expert on doubles; however I would go for the 9.3x74r. The problem with 45-70 is that is a slow / week round compared to the 9.3. I have friends that lode the 45-70 up to unbelievable velocities and regularly take moose in Alaska with it. However, they are using the Ruger #1 which is with out a doubt a much stronger action than the Pedersoli's Kodiak rifle. In MHO save your self some trouble and go for the round that is proven to work and does not need to be “modified” to work. I think that you will be much happier in the long run.