Muskie Hunter,
I have a Leupold 1.75-5X mounted on my GG. For me, it's an ideal setup. Now that I need bi-focals, my iron sight days are just about over and the low powered variable just fits my needs.
I initially set it on it's lowest power for a wide field of view for closer shots, but can crank it up for longer distances. 5X is plenty of power considering the 45-70's effective range.
Best of luck with your choice. I'll bet your going to enjoy your GG.
Best,
TnNuc