For anything over 1/4" in spacing, you'll need to either install longer studs, or buy a spacer of a "bolt on" design (bolts onto hub, then wheel bolts to spacer).
Your factory studs should stick out 1". If you buy the bolt on design, keep in mind that the factory lugs are going to stick out farther than the spacer and could interfere with the rim unless your rims have recesses in them like mine.