OEM starters are recommended for ease of fitment. It is very important that the tooth count (153 or 168) of the starter match the tooth count of the flywheel to ensure proper engagement. Two primary options: a 12 3/4-inch flywheel (153 teeth) where the nose cone will have two attachment bolt holes across from each other (inline) and a 14-inch flywheel (168 teeth) where the attachment bolt holes will be offset (diagonal). This applies mainly to factory GM starters on passenger cars/light trucks and does not apply to later model versions (w/ gear reduction) or aftermarket and mini starters. Be sure to match your clutch to your flywheel as well.