I recently tried to get matching keys for my '68.  As you know the locks are unique to this year.  My ignition had been changed so the key would not work my door locks.  I removed the door locks then using the code on the lock cylinder, cut new keys.  They are the same type of key as the ignition, so I identified the ignition by having a key wraped in rubber and the doors a plain steel.  Good luck on finding a lock set.

The '68 ignition cylinder comes out with the key & a the point of a paper clip.  New ones are available from Advanced for under $20.