slant question as to years.

I thought the change to the larger register hole in the crank was 1968, but many posts here to search. I recall that sometime in the 80's, they renamed the transmission from A-904 to A-999 or such, but I think still bolts to a slant six. Those probably have lock-up torque converters and other features for better mileage. I saw a Navy van at PickNPull with a slant and fairly new-looking tranny. It appeared to have an electronic pickup where the speedometer cable usually installs. Didn't get the number.