Hi, Buzz here. 2 thoughts:
1. Try the Hiller museum at San Carlos airport. I forget what they call it now, i move out of the Bay Area 10 years ago. Somebody there might have a few more clues where to look.
2. There was a book at out local library (Vancouver Wa) called "Lockheed aircraft since 1920". I don't see it available in an aircraft books catalog.
More thoughts: You might try a web site called VPNavy.com, it's about naval patrol aircraft. Most of them were Lockheed.
Let's see, i was a crew chief at Travis AFB in the early 80's, most of the airplanes (Lockheed C-141's) i took care of had 64 to 67 (fiscal year) serial numbers. I don't know what the C-5's had.
For fun i used to crew chief a 1945 Lockheed PV-2 Harpoon, we'd fly it to local airshows. Lockheed makes a good airplane.
Good Luck! Buzz Fuselsausage: Line Mechanic by night, DC-3 crew chief by choice.