Help, 72 duster NSS/Back up light harness hook up.

Hi, i have a 72 Plymouth Duster. I'm working on my NSS harness now. It is on an auto trans. My harness is good from the transmission up to the 3 prong connector that plugs into the bulk head, but i can not find the plug to plug the NSS harness into. Any ideas or anyone have a 72 that could tell me where its normally at or where to look. It would help tons.
Any suggestions
Thank you.