Ford Diesel Fuel Tanks
Ford produces some great fuel tanks, but as all parts of all cars these won't last a lifetime. If you like to research, find and get the best parts, you can find some cool aftermarket stuff, which may even offer more features than your stock parts.
One of my favorite reasons for changing fuel tanks in Ford trucks is capacity. If you look at the Transferflow website you will find replacement tanks with added capacity for trucks from 87' to '08. There's a model with a 60 gallon capacity, which will probably take you half way around the world and back! This won't cut your fuel costs but you won't have to worry about refueling all the time, perfect for long family trips.
While not strictly a replacement fuel tank, you can also get a refueling tank, which can be spiced up even more with a toolbox combo. I found a cool one on performancedieselinc.com which can give you as much as 100 gallons extra (plus tools), making you a mobile gas station.
In the end fuel tanks are fuel tanks, so there won't be a huge load of variations on features, but durability and life span makes a big difference. If you want the lowdown and the best products take a look at popular forums like the Ford-Trucks forum and search Amazon or Craigslist