I forgot to mention that I have the part numbers in my 1965 Passenger Car Catalogue (Canadian), if they would be of any help? They are not sized just part numbers.
[ame="http://www.ebay.com/itm/25-Well-Nuts-6-32-Thread-452-Head-Dia-/121137441897?pt=Motors_Car_Truck_Parts_Accessories&hash=item1c345aac69&vxp=mtr"]25 Well Nuts 6 32 Thread 452 Head Dia | eBay[/ame]
From what I see these are the ones we need. I have checked out my old ones and I can see the WELLNUT letters casted in the rubber. But I'm not sure about the threads!!