Rear cross member assembly plant code

[mleder]

With in the last 2 years I seem to recall a discussion on here where on some frames we see a code that designated spring package and the plant where it went down the line. For example my 30 cc pickup has pu occ stamped on the right side of the rear frame member as you look forward from the rear of the truck. Would someone have additional information on what each code designates. I was told my code relates to the Twin Cities plant (Minnesota)