Hello,
The intake FAQ
here basically confirms that you have what you say you have. The "393238" casting number and "F" ID code both coorespond to the L-69 manifold.
As to the date code: yes the code is a Julian date, which means it is the 151st day of the year. However it does not tell you which year. I'd also guess that it was 1966, so that means that it was May 31, 1966.
Tuesday, May 31.
Nice weather in Detroit that day. Mid 50's, partly cloudy. Not much breeze.
I don't know what the "AZ" means. I will leave that to the experts on this forum. The ones who actually work on the cars, and don't look up historical weather data just for kicks
