78z drivers side door key lock sticking.  I can not lock or unlock my drivers side door with the key.  When i turn the key it will only turn half way when i try opening or locking.  The door will open and lock with the door sill knob but not with the key.  is there a fix for this or if it needs new parts are they available?  THANKS!      

Have you taken the lock out? Pics? Sometimes just removing and cleaning will help. These old locks just wear out sometimes.  You can source replacement locks from ebay, but I've never used them and cannot attest to their quality.  A quick fix, if you needed to drive daily, would be to swap locks with your passenger door.  Sorry, doesn't solve you problem though.

There have been several discussions about your exact lock problem in the past. I can't spend a lot of time searching right now, but if you do some digging and searching here about locks, you'll see threads that talk about that issue and some ways to fix it.