Detailed photos of the 2.8 RSR heads as received, prior to restoration. Casting p/n https://pbase.com/9146gt/image/151079278 and casting date code 1/73 https://pbase.com/9146gt/image/151079282

This set of 911 RSR at one time were redrilled to be used in either a 2.8 or 3.0 liter crankcase. Note the oval, elongated stud holes https://pbase.com/9146gt/image/151079278 on each of the heads. From a mechanical point of view, redrilling and spacing outward the stud holes on these heads does not create a reliability issue.