While in Monterey I picked up a trunk lock along with a functional door lock and key from an owner. Task- rekey the trunk lock to work with the doorkey.
Sure enough, the key failed to rotate the trunk lock cylinder and I set about removing it's retaining pin to access the bare cylinder.
Removing the pin was unusually problematic and then getting the barrel out of its housing was amazingly difficult, only finally releasing its grip when thoroughly soaked with non-oily lock lubricant.
When I inserted the key to observe how many of the pins were not remaining flush to the cylinder surface, I saw that the key was already a perfect match for that cylinder.
Lesson to be learned here?
When a 45 year old Pantera trunk lock fails to rotate in it's housing, the culprit could likely be 45 years of exhaust and road particles jamming everything together and not a matter of a mis-matched key.
Thought I would pass this on to others who may face a similar situation with their trunk locks.