okay, let's see.. like several have said, unless the Marlin really has some age on it I'd be surprised if it doesn't have a grooved receiver. Rugers come with a removable base from the factory (4 screws) I replaced the base on mine and it does now take Weaver style rings. Weaver style rings are wider that those for a grooved receiver. Not a thing wrong with a Marlin 60 but the Ruger has arguably the best removable magazine ever made. Depending on what you get Rugers, Marlins and 597s all tend to shoot comparably out of the box. All or any may be picky on ammo - in fact they are likely to be. While the mods on Rugers are limitless there are mods you can do on both Marlins and (especially) 597s to get them to perform better. One thing - the 597 is a "man-sized" rifle while the Ruger and the Marlin are more "carbines" and probably better suited for kids. As far as scopes I don't think you can beat the Nikon ProStaff rimfire series. Great for the money.

One of the rifles I built is .17 Mach II.. Possibly the best squirrel cartridge ever built but for general use, I'd still stay with the .22.