There is really no bad news on the motors, but there are some things that you should know before you go buying any '03. Get an Oasis Report from your Ford dealer and that will show all of the work done on the truck by Ford. You want to look at the engine work for head gaskets, or EGR work or EBP sensor work. Or any other major repair (and this goes for any truck or car). How many miles on it? The Torqueshift will run some bucks to get rebuilt, but nothing special now that they have been out for a few years. Good Luck.
If the truck runs good now, it will run good tomorrow. They had some teething problems, but they usually show up in 30 - 40,000 miles.
Dave