Since nobody has responded to this yet, I will. I'm not sure whether all of them came with a lock . . . I suspect that they did. The right people to ask would be the CRPL - Corvette Restoration and Preservation List.
I faced the same question lately on my '75. The lock was there, but I couldn't open it. The door key did not fit. After considering cutting the lock off with a hacksaw, I instead re-keyed the lock - easy to do with a couple of common tools.
Anyway, I can't answer your question, whether or not they all came equipped with a lock . . . but it is certainly worth the 40 bucks from Dr. Rebuild for the peace of mind . . .
82-Guy, all 63-82 Corvette's came with a lock (covered with a rubber boot) on the spare tire carrier. You should be able to get it from Corvette Central. Also, I think that it was keyed differently than any other lock on the car.
Thanks for responing, guys. I just got hold of the NCRS manual. It states that the spare tire lock was not available for 1980-1982. If a spare tire lock is installed, deduct 6 points. I was all set to buy one since I thought it was missing. Just like we say at work - read the manual. Now if I can just find that RC-33 radiator cap nobody carrys anymore.
My '81 has a spare tire lock just like the one I had on my '72. This intrigued me so I called my buddy the original owner and asked him if he ever put it on. He claims it came from the factory (St. Louis) with the lock attached, and it definitely looks like its been under there for 20 years. Interesting. I'm going to keep digging a little.
Maybe the NCRS should add the old "investigation continues" line. I did not get any points taken off at the judging. I just thought they all came with the lock. On the other hand, since this was a one-owner until last fall, it sounded odd that the guy would take it off and not put it back on. But then again he replaced the radiator and overflow caps with cheap replacements.