Pretty sure it is original to the truck.
It looks, in construction, just like this NOS one. Tack welded where the vent meets the blower housing.
http://www.flickr.com/photos/advance-design_parts_co/8129330842/in/set-72157631868452754Rather than this one that is screwed together at the vent and blower.
...otherwise it looks just like this one, same decal, same shape, but darker paint...
http://www.flickr.com/photos/advance-design_parts_co/8129370166/in/set-72157631868452754I'll post a pic in a couple hours when I get home.
...I'm going from memory here so I could very well be completely wrong...
