911 RSR 3.0 Liter Twin-Plug Factory Racing Heads - Set 3 (Stratton)
This set of 911 RSR were redrilled so that they can be used in either a 2.8 or 3.0 liter crankcase application. Note the oval, elongated stud holes on each head. From a mechanical point of view, redrilling and spacing outward the stud holes on these heads does not create a reliability issue.