I have a 1986 f 350 automatic. The key has been getting difficult to turn, and now I can turn it, but it will not start. Tried to?

Try squirting some WD40 in the keyhole

Look up: ignition rack, actuator. Those are the parts failing. I'm sure there are some you tube videos even. Column work is not for the novice. I'd consider replacing the ignition switch and lock cylinder while I'm there if it's all old.

If you remove the plastic cover around column you will see a rod on the very top of column. Latch a small pair of vice grips on that and push down to start, pull up to stop. You may need to turn key simultaneously.

Replace the key cylinder. It will come with a new set of keys of course.

The tumblers are worn out, the key switch needs replacing.