Thank you for the picture and the explanation of the hose color! It does explain the issue.
That said, I did join the H/O club and they did say that the car is number 1014 build of the 3500 and built 6 Jan 84. Strangely enough, it was bought in Sanford, florida. The clittle corrosion indicated does not indicate a northern car. So, I don't know why it has the plug. My hope was that if someone ordered that special piece of kit, they might have also optioned the posi, but not to be! Before Atlanta, I believe it resided in Kentucky. Further, the CarFax doesn't go back far enough. I think it stopped in the early 2000's.
So, I think then, I need to hook up that hose to that third nipple presently covered by the plug...if I understand the conversation and conclusions. Whew!
Oh, and no driver door tags. I had to have those reproduced. The car has been repainted but I have no clue why the tags were removed instead of being covered.