The pins are secured by spring steel push nuts, which can be a PITA to get off. If you can take a propane torch and heat them cherry red, they'll bend a lot easier. If you can't use a torch (already painted truck), then you'll just need to pry them off using the brute force method. Or maybe if you can get some nippers in there, you could cut them loose.
One of mine had rusted completely away, so that was easy.
Good luck.
