Nice looking gun. For a hunting/working gun, the marlins are hard to beat. I like the old pre-angle eject winchesters for the nostalgia factor. You got a good deal. I'd keep that scope, put the lowest mounts that will keep the bell from touching the barrel(may have to remove the rear sight) and not worry too much about the variables. All my hunting rifles have a 3-9x that gets set on 4 or 5X and left there. The only reason that I turn mine up is at the range, or to get a better look for antlers on whitetails(and for that I know I should be using my binoculars...)

Good luck