I have found two different casting numbers on these package tray plates. C8ZA-18C491-AW and C8AA-18C491. The C8ZA plate is molded straight on the one edge. Was this C8ZA plate only used on the assembly line for a period of time or only in Dearborn or San Jose? I find the C8AA, 5 to 10 times more often.
There also seems to be two different styles of switches for 1968, is that because some were dealer installed? all black and more deluxe with chrome knob.