I believe the change in distributor gear material coincided with the switch from steel to cast iron cams at the same time the cam bearing diameter also changed. That would have been in 1954 or so. The steel cams with the small diameter bearings were used in the 216s and spray-oiler 235s.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!