'67 and earlier cranks had a smaller convertor register, which required a smaller nose on the torque convertor. I'm not sure about the 727s, but I know 904s also had a different input & spline in those years which would not allow swapping convertors between the two age brackets- I would suspect a similar situation with the 727.
In other words, I believe what you're looking for would be a '66-'67 727 to mate to your '65 383.
If I'm incorrect in my assumption I'm sure someone will pipe up!
