You may just need to remove the ignition and clean it and use a little graphite as suggested above.
If your door lock is original it will have the stamp code on it.(as Cletis posted)
...pic... I took my door lock and a different original ignition I purchased from a fellow bolter to a local lock smith and he keyed them alike for me. I think he charged me 40 bucks.
My truck is no longer keyed to the code in that pic.
