bigboresixguns
I too would like to welcome you to AR. I have used the 45/70 a fair amount. I have shot several deer with various 300gr. bullets, the 400 gr Speer and the 350 gr. Hornady RN.
The 350 Hornady is my favorite bullet. If you do not reload the 300gr Nosler Partition, the 350 gr. PMC or the 350 gr. Cor-Bon would be my choice for factory loads for deer and black bear.
As for a scope the Leupold 1.75x6 with the Heavy Duplex would be an excellent scope for your 45/70.
Do not let ANYONE tell you other wise... with the proper bullet the 45/70 is the HAMMER OF THOR for any North American game at up to 150 yards.
If charged by a Kodiak Brown Bear I would rather have a 45/70, with the right bullets[Garretts Hammerheads], than ANY 375 H&H.