Like all ignitions the CJ-7 key simply pushes a metal rod that is connected to the plastic wiring terminal located on the lower portion of the steering column. This connector controls the following positions OFF/ACC/RUN/START.
Something must be rubbing against this rod to create the friction causing the hard to turn problem. Take the cowling off that is attached to the dashboard and the steering column. See if you can see the problem.
I doubt it is in the lock cylinder. Even if it is, changing the key cylinder is not hard to do.