Photos can tell the story better AND also raise a few questions. The 3 slit water pump evolved from prior Oscillator type pumps into a Vane type pump. Some parts shared some parts not shared. All will work on any model or year so long as the gear set is correct for single or twin. Factory offered a kit to convert all models to Vane typpe water pump, Note that some models did not have the rubber element clutch and some owners converted to sheer pin. Drive shaft has extra hole to allow for either.