Marlin Guide Gun in 45-70 govt.
I have one of those. It's a very nice rifle. It pairs nicely with my BFR revolver in 45-70 with 10" barrel. The downside is that the BFR is limited to loads of 31,000 PSI per the gunsmiths at Magnum Research. The Marlin rifle is rated for 40,000 CUP.