I have the older ruger varmit with the Med-weight barrel with tang saftey it wears a 3-9x40 Redfeild Classic.I also have a Ruger No.1-B that has a 2.5-10x40 Simmons.I use my 25-06's for coyotes and deer and antelope.
I think anything 3x9 or large should work good,maybe a 4-16 or something like that if you plan on shooting ground hogs.