Well, your 2000 Superduty doesn't have PATS, so you don't have to worry about the electronic side of things.

I think you should be able to pop the ignition cylinder (it's very easy), bring it to a locksmith and get a key made to order. Or at least, figure out why that cylinder is giving you trouble. It works in the doors OK?

This is one of the reasons I always keep the original key tag from when I buy a vehicle new.

To remove the ignition cylinder, put the key in, turn it to almost the ON position, put a small phillip's head screwdriver into the hole in the plastic cover under the cylinder, push up, and VOILA, the cylinder comes out. Look around on here for more information on how to get it out. Not sure about how far you have to turn it.