Not sure I can help you as my car is a 1930 Durant 614, but I will share my experience with the tail light plug issue.
My plugs (connectors) are the 2 pin type and are made of bakelite. The originals crumbled and I looked everywhere for correct replacements. Thought a Ford Model T connector might work, but all the Model T guys said no. After months of searching I found a specialty place in CA which had excellent reproductions. Bought an extra set for spares! Later found out the Model T guys were wrong and the connectors were available (they just did not handle them so were not knowledgeable).
I bought my connectors from Jessica at Restoration Supply Company Inc. in Escondido, CA back in January, 2017. Part number for my 1930 Durant connector with 2 contacts is ELE141. The part description is "Plug-Bakelite Double Contact, screw on ribbed cap". The connector has two evenly spaced retainer pins on the sides, and internal screws under the screw on cap to connect the wires from your wiring harness. You can check their website at www.RestorationStuff.com. Cost is about $16 each, but no matter since they are available.
Robert, Just to let you know, I was able do some build-up work on one of my existing double pin plugs with J B Weld enabling me to carfully pull out the locking pins and relocate them to a position which allows locking the plug into the tail light socket. Works like champ. Still need a license light lens if you know of anyone who has a spare kicking around. Thanks for your response. Curt
Where Are You From? Denver
Do You own a car built by Durant? 1926 Star m 4dr sedan