Going from a family hauler Excursion to an extended cab truck will be quite a bit different. If your not going to be carrying people around in the back seat I wouldn't worry about that part however with any vehicle second hand especiall the 6.0 either inspect it good yourself or get it inspected by a reputable shop. Unless your prepared to spend money on one.
At the same time its like what Micheal said in your header thread save the money for a diesel.
99 F250 CCSB V10 4x4 Lots of money into it.