Per the GM Heritage Center the Van Nuys plant is listed in the 1946 Truck Specifications. Can you share where you found that it opened on Dec 1, 1947. I find it hard to believe Van Nuys made a Model "OS" (1946 first series 1-1/2 ton truck) in 1948 after the AD's had been introduced...
Mike B

I have listed several links to the Van Nuys plant opening in December of 47.
As for the 1946 data book?
LA timeswikipediawikimapia.street muscle magIn MDReed third post he ask about the MASTER on the cowl tag. I found a tag like his truck, (42) 1-1/5 ton, 160” WB with MASTER on it to show him. I thought he would ask about the 42. And that is just a guess. I was not thinking about Ozark45 post.