<VV> Late model steering box housing numbers

[66vairman at comcast.net]

Hello everyone: 

Is there any way to determine the year of the 1965 to 1969 steering gear boxes. It appears most of them have a casting number of 5678921. Under this number then, is a single digit ( I have a '4' on one and a '9' on the other). Under this number then is a two or three digit number ( I have an '89' on one and a '151' on the other). Is the 2nd row single digit possibly the year of the box? Thanks for your responses. 

Tom Rahochik