When did Chrysler switch from chrome to plastic A/C vents?

There is a difference in how those plastic duct assemblies marry up to the main plenum. Not sure what year they changed. Not easily adapted.
The small rectangle adjustable louver sections are interchangeable throughout the years. So when the pot metal louvers became pitted/broken one could just swap the black plastic ones in. I had considered sending the black plastic ones along with a group of other parts going out for vacuum metalize chrome restore. I learned that air flow would take that type of chrome finish right back off again.