I have always wanted a single shot in 45/70 since watching Quigley down under...I am a left handed shooter that is one reason the 1885 browning peak my curiosity.
If you want to be "Quigley" you need an 1874 sharps.
I have no experience with the sharps replicas, but if I was in the market I would be looking for a Shiloh or a C sharps.
...and fortunately for you it appears that the answer to all of these observations goes up for auction next weekend (
Click Here). It's almost like a sign from above that you should go buy this rifle.
Seriously though, as a left-handed shooter too, I do have a Browning 1885 chambered in a smaller .44 Magnum with a similar round to octagon barrel like the BPCR that I like a lot (pictured below with my gunsmith). I shot a deer with it a month ago during Mississippi's primitive season & it worked great. I also have a much larger Winchester 1885 Safari Octagon in .375 H&H and a Traditional Hunter in .405 Winchester. All of these are excellent rifles that I really enjoy shooting a lot.