Any idea…

[Monacooo]

What is the purpose for the plug in the picture?
Car is -74 monaco custom

Also I would need wiring diagrams for this car.

 

[CBODY67]

Wiring schematics are in the Chrysler factory service manuals. They can be free-downloaded at www.mymopar.com. Once downloaded to your computer, you can enlarge them for better use, if desired. Then, if desired, you can also take a screen shot of the enlarged page with your phone for even easier viewing.

What wiring issues are you wondering about? Just curious.

CBODY67

 

[D Cluley]

This is just a guess, but if that yellow wire just loops back in the connector, then I suspect it is to bypass the seatbelt interlock system. I remember doing something similar on my '74 Dart.