I have always had a top on the back of every pick up that I have ever owned and wouldn't be without one.
We just bought a new 2014 Dodge last year and the very first thing I did was get a fiberglass one. They will match your truck colors exactly.
I also got the tracks built into the roof that accept Yakima racks.
In it, I carry two mountain bikes, all of our back packing gear, all of our snorkeling gear and all our paddling gear for two kayaks and a canoe along with a bunch of other stuff. It all stays nice and dry and locked up.
jack L