Radiator cover panel bolts / nuts?

[Advanced Design]

This is a really basic question and I haven’t been able to find the answer, so I figure our group here will know.

The radiator cover panel, in this case one for a big block radiator, is secured to the radiator core support with four bolts. Picture with bolt holes circled below. What type of nut was used to secure the bolt? Was a cage nut used?

The nut will not be accessible with the ac condenser and panel in place, making it necessary to remove that to remove the radiator.

Granted, I will make something work, like tacking in a nut to make removing the radiator easier. What did the factory use?

Thank you!