I usually pound a putty knife / paint scraper under the edges of the plate to raise the nails far enough to grab with vice grips so you can twist and pull them. Often the metal plate will get bent up a little, but it can be pounded flat again by putting it face down on an anvil. You may need a lot of prying/force to get the nails to move.
if you're refinishing the side rails, you'll need to remove the plates from okoranges rail to refinish that as well.