Thanks, I tried the National Air and Space Museum, who then put me onto the National Archives and Record Administration. They do hold the two drawings in question, F-1002 (#2 Bulkhead) and F-1003 (#3 Bulkhead), unfortunately the rights for these drawings are still held by Northrop Grumman. I contacted the person recommended by the NARA to gain permission to get copies but it was refused due to possible liabilities against Northrop, so I am back to square one. I will now make contact with the San Diego Air and Space Museum and see if my luck is any better. Thanks for the help.