UPS has been using Aluminum for years, and is now looking at plastic.
http://www.whatisworking.com/2011/06/ups-trucks-made-of-ultra-light-material.html
-——is now looking at plastic.-——
I would think fiberglass reinforced plastic would be an option. The big rigs now have FRP cabs and seem to do ok. They don’t get knocked about like pick ups but I don’t see aluminum doing much better for getting beat up and knocked around.
I wonder if they mean something like high density polyethylene? That material is both strong and very tough. It will not however take a decent finish.
All those Postal vehicles are aluminum as well....Really ugly when they catch on fire...