The correct pillion saddle would be an "Acumen" Long or short version. You would be best to speak to Jan about these on wd.register@gmail.com
Which means the NOS cover you bought is wrong. Below is one of the long versions. The nipple that you asked about by the foot rest is for the front loop of the rear stand spring. Ron
The best thing is to start here on the forum with the frame and engine number...That will determine the year of manufacture and contract that the bike was built under...From there a specification can be determined and you can then deduce what you have and haven't got...
One clear photo of each side of the bike will serve for an initial assessment of its condition etc...Ian
PS I think you might do better to start a fresh thread with individual questions and pictures to save trolling through this thread which might put others off. Ron