I have a 37 2 dr Town Sedan. In process of restoring, so have a bare wheel. Just measured and here is what I get:
Overall outside diameter 17 1/2. That is not where the tire sits, but the absolute overall outside diameter.
Overall Width 5 3/8. Again, not where the bead sits, but the overall width from outside rim to outside rim.
Not real sure what you mean by/ "backspacing" I placed a straight edge across the back side of the wheel then measured from the straight edge to the bolt hole from the back side. I get 3 5/8. If you need different measurements let me know and I can get them for you quite easily.
Ron