Marty: The base for the stanchions was an extrusion. I would suggest that you do as Rick suggested. Just remove one of the existing ones and take it to a machine shop. Depending on the cost, you may want to have several of them made and sell them on this website. I believe that this part works on the 31, 34, 37 & 40 for the same years.
If this cost is prohibitive you may try searching all of the salvage yards in your part of the country. If you find a boat that has them get them all, they are very difficult to find.