I just did this! You my friend are in luck, I was discontent at first the general reply was to just have a different key to open your door, or my other option was to "just to rekey." Sigh. I didnt want to, and I didn't want two keys! I just want stock, plain and simple.
If you have the ignition key (should be keyed the same as the doors) you'll need to find the key code stamped on all door locks or their mechanisms. See attached photo for reference. Note if you have a locking engine lid, not to go by this code as it was a dealer option and prob was keyed to match your main door locks.
Once you have this you need another chamber preferably the same year as your bay, my early is a '69, I got a door handle from a 70 and it was designed differently. Had no set screw but with a little re-engineering I managed to make it work!
Once you get the tumbler and have the key code you can get a fresh key cut and have a lock smith re-tumble your tumbler.
Then put it all back together do use lock tight on the lock portion my first time through I did not, and after a couple unlockings, I heard a plop in the bottom of my door. :roll: had to go back jnto my door get it fix it and do it again.
Hope this helps fella!
-Eddie