Torque Converter ID

Is there a difference between the keyway on a 904 vs 999 torque converter? Reason I ask is because the purple torque converter that I’ve had laying around for years, thinking it was for a 904, will not fit in what I’m pretty sure is a 1985 999. Look at the difference in the slot sizes of the two (rusty one is the one that was in the trans). Is my purple one actually for a 727, or are the earlier 904 converters just not interchangeable with ‘80’s 999?

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