Depending on the conditions the car may see after restoration may guide you to a choice during restoration. Of course the your choice on how to clean the rust off also has a bearing on it also since blasting (for example) will leave a finish who's surface texture and color are unlike any natural metal. If you can clean it and return it to a factory look then protecting with a coat of Bo-shield (or similar product will work) after you paint the face like factory. Others would add a coat of stainless steel paint (or one of your likely that reproduces the look of bare metal ) then paint the surface
This basically applies to all mustangs (and cougars
no matter if the dash section is removeable or is welded in. Just another challenge
