[rotorwrench]

Ford started the change over to the new transmission on the Mercury cars sometime in late January or February of 1951. Both of my 1951 cars were manufactured in November of 1950 so they still have the early style half bell set up. 1951 was the change over to the new diamond cut gears that were a improvement over the older gears since they have a wider tooth face profile. Ford likely wanted all the cars to use the same basic transmission & bell housing and that came to pass in 1952 for Ford and Mercury cars when they all went to swing type pedals.