I've no experience with that exact bullet from LC but I have tried their 44's and 45's and they are good bullets. I would expect their 45/70s to be just as good.
I have a Marlin GG and it works great with .460 boolits. I have found some commercial 45/70's to be .4575 so check whatever you get with a caliper to make sure. The PMC 45/70 cowboy loads (ammunition) is .457 also. You don't want to run .457 through your GG, ask me how I know...