Can anyone provide a credible source for decoding the cowl tag of a Los Angeles built 69 Camaro?

This is a good site: http://holisticpage.com/camaro/parts_fs.htm it should answer all your questions.

A '69 Van Nuys car won't tell you much from the tag. Interior and exterior colors and when it was built. The code to the lower right is a sequence number that won't tell you anything.