I'd go with media blasting...sorta like sandblasting only they don't use sand. Sand can warp the sheetmetal. Contact a couple of your nearby powder coating operations and ask them who they use for media/sandblasting. They should be able to tell you who can set you up. It probably won't cost you much (yes..I know..a relative term)..while you have the box off, I would take the big plunge and pull the cab too. Powder coating the frame in our area can be done for as little as $200.
