I had one of those panels, with the 'F O R D', instead of the emblem on my 87' xlt. It was dented and had a white film on it that, I could NOT get off. The only thing I found that seemed to soak into the film and make it more 'see through', was thin oil, like wd40 and the like. So I looked into a new panel, even then (about 10 years ago) they were obsolete from Ford, but it showed a list price of somewhere around 600 or 700 dollars!!
I found a used one in very good condition for a lot cheaper and started getting it ready for after I had the truck painted, but never did and sold it with the truck. One think I did, because that panel being in contact with the paint and collecting dirt and being moist started corroding and rust started on the tailgate, just behind where it made contact, is I bought cork chair bottom protectors (similar to these here -
http://www.globalsources.com/gsol/I/Furniture-felt/p/sm/1060437395.htm#1060437395) cut them in half and stuck them on the back of the panel with the rounded side facing up (so water, dirt, etc. would run off), everywhere there was pressure from mounting brackets, screws, etc. So, to give you an idea, I used probably about 16 or so. And if you do that, make sure you keep them in far enough from the edge, so that when the panel is mounted, they can't be seen.
Some newer Ford trucks have a newer panel similar to these.