From somebody that's done this on several different trucks let me just say that you've got your homework cut out for you.
What is the purpose of your truck and what is the "look" that you want?
Do you ever plan on hauling anything of any size? If so, then you may want to consider a sliding top. They make an electric sliding tonneau that actually has a small built in tool box at the front of it.
Do you want it to lock to the tailgate?
Are you looking for a high profile or low profile? Here's a pic of my Silverado with the lowest profile lid I've ever seen...water tight and it locked to the tailgate...


and the company for that lid.....
http://www.stslids.com/You might also want to consider a heavy duty rubber bed mat to keep things from sliding all around under there.....money well spent wether you have a lid or not.

A number of other selections....
http://www.campway.com/products/lids.html