There's a reason the 6.0 and 6.4 Ford diesels are so cheap used. I toyed with the idea of buying one and then bulletproofing it but in the end I just didn't want to deal with it. I don't know what sort of budget you are working with but I would look a little at new trucks too. I started out intending to find a used truck but the prices were so silly it made sense to go with a new truck instead - it takes a lot of years/miles to get much of a discount from new.
Edit - it doesn't sound like you need a HD truck but you might like one. They are heavier built with stronger components. The only real downside is a stiffer ride (and poorer fuel economy if gas).
