The Robar finishes look nice but seem rather pricey for a "truck" gun. The Birdsong Black-T might be the way to go but I don't know if it can be applied on aluminum. http://www.black-t.com/index.htm.
Even cheaper, buy a can of DuraCoat for a painted finish or their "shake-n-bake" finish. They apparently can be applied on aluminum. http://www.houtsenterprises.net/index.html
Even cheaper, buy a can of DuraCoat for a painted finish or their "shake-n-bake" finish. They apparently can be applied on aluminum. http://www.houtsenterprises.net/index.html