FireBob, if you want a good durable finish - but not original - check out Rustoleum hammered black or gray paint. I got it at Lowes by the quart and used a brush to apply. That stuff is tuff as nails! I used two coats. And very reasonable cost. I used this on my Plymouth.
On our bird I had the underside sprayed with the rubber type truck bedliner. Wish I hadn't. Just because... no reason other than that, I just wish we hadn't.
There are some more expensive options available, "Chassis Black" comes to mind, I think available at Eastwood or auto paint shops. Cal