Door mirror screw inserts

[tucsonjwt]

I bought my 83 C20 many years ago and it came with holes in the doors for the old style tripod mirrors. The mirrors were not with the vehicle but the holes are still in the doors. I just have the standard 81-87 mirrors now.

I found what appear to be the same style swing out style tripod elephant ear mirrors at the junkyard. The mirrors look OK to me, but I can't figure out the threaded inserts on the doors. There appear to be threaded inserts with 4 metal tabs which crimp over the inside of the door skin. I can't figure out how those are secured. It must be some special type of fastening tool. I tried to pry the ears up but they are on there tight, and I can't see how I could get to most of them from the inside of the door.

Does anyone know what these inserts are and if there is a special tool to install them? I already have the holes in my door (except for the two holes which I think have the factory inserts under the current stock elephant ears. If I reuse the those two inserts, that would leave me with 3 holes in each door which would need need replacement inserts.