There are two things going on when you put in the key and start a 3rd gen... There's the obvious mechanical lock in the steering column. And there is also a chip built into the plastic part of the key ("PATS" I think) that must have an electronic code registered in the PCM or it won't ever start. Long story short, if you replace the ignition lock with new (along with a new matching key) the engine will turn over but it will never start.
The ignition lock is amazingly easy to remove (see below), but the $278 that the Stealership gets in labor is mostly for reprogramming the key to electronically to start your truck. Still a rip-off, but you need a very expensive computer widget to do this. A high-school shop class student could do the whole thing in 30 minutes if they had the Ford computer tool.
My advice - don't buy anything. Call an honest locksmith. Tell them you have the title for the truck, or as an alternative the registration in your name to prove ownership. They will be able to re-key a new lock cylinder so your existing keys work and start the engine.
By the way, to remove the ignition lock, first remove the bottom plastic steering column cover (3 small bolts). Turn the key to 'RUN'. Then take a screwdriver and push up on the small nub directly underneath the lock cylinder and it all pulls right out.
I don't steal cars, but I do buy them at auction. Most have either mis-matched or hosed up ignition locks.
