the part number I used was Oldsmobile part #6280765 from a 66 printing of the parts catalog. this number crosses to Auveco 3617.
the slot for the nail is extremely tight on these, take a bit to get them in and I am sure if I need to remove the panel the clip is coming out of the door. But it is all I could find.
https://shop.northlandfasteners.com/...met-N03617.htm
https://www.clipsandfasteners.com/Do...et-p/a3617.htm
https://autobodyclips.com/product/3617/

 

 

This fastening system is used on early 60s Chevies, so every Chevy repro vendor sells both the plastic sockets and the "nails".