Given the relative scarcity of usable plate holders with film sheaths inside in that format, I probably wouldn't toss them without trying to clean them up first. I'd start with a stiff wire brush.
You're almost certain to knock off a significant amount of paint, so first remove the film sheaths (with them, you'd use standard cut film, without you can order dry plates from J. Lane, who is a member here). Get the white stuff down to bare metal, apply a zinc chromate primer for metal, and then paint with a matte enamel to (fairly well) match the original black.