1958 thru 1964 FE's used a 153 tooth ring gear with a 'forward pull' bendix on the starter. 1965 and newer FE's used a 184 tooth ring gear with a 'rear push' bendix on the starter. The ring gear pitches are different between the 153 and 184 tooth ring gears which means the starters need to be matched up to the appropriate flywheel/ring gear. The ring gear register on the '58-'64 standard flywheels is on the engine side of the flywheel so that the ring gear is not pushed off of the flywheel by the starter working forward. Likewise the ring gear register on the '65 and newer standard flywheels is on the transmission side of the flywheel. Ted Eaton.