1969 RIVIERA STEREO RADIO WIRING DIAGRAM

I am trying to test a 1969 Riviera AM/FM Stereo (with the separate box) but I need to know where the wires go.
There is the normal 3 blade connector on the main unit & another blue wire pigtail coming from what I believe to be the stereo box.
Any help would be greatly appreciated.
Thanks in advance,
Doug

 

https://www.teambuick.com/reference/library/69_chassis/files/120-127.pdf

 

Roberta, Thank you just what I needed!
Doug