Plugging holes in truck bed?

Quickest would be snap in plugs available at hardware stores. Plastic or shiny plated metal. You could seal them with a dab of silicone.

I was just looking at the bed of my Comanche yesterday. I believe it was a work truck when new and there are multiple 1/2" holes filled with deteriorating bondo in the bed. There are 2 about 1-1/2" dia in the left wheelwell covered with plates attached with sheet metal screws. It needs new bed lining so I'm going to clean all that out and weld in flush metal discs.