I began work at the Laboratory in February 1984 for the Zia Company as supervisor in the Engineering Department. In our custody were all of the engineering documents from the Zia Company.
These were stored in flat file drawers in TA-3, SM-38. Later they were moved with the department to the Pueblo Complex. I do not remember seeing any drawings on the Post Office Building, as the recent correspondent said it was built by the Zia Company and McKee Construction Company.
All of the Zia records were transferred to the Laboratory Engineering Department in TA-3 after I left the Support Services Subcontractor in 1989. If someone wants to find those historical documents, that would be the first place to start. Also, a search of the Laboratory archives may find relevant documents on the Post Office design and construction.
Later in the 1990s, I was employed in the Engineering Department in the old school building on Arizona Avenue. We received a request for a legal description of the Laboratory boundary. Original documents from the Laboratory along with DOE records were used by a consulting firm to prepare a boundary description of the Laboratory.
The DOE archives that were at the old DOE area office building in Los Alamos, could be another source of information on the Post Office construction project. The Zia Company was supervised by the DOE office until 1986 when the contract was transferred to the Laboratory for the new Support Services Subcontractor, Pan Am World Services, Inc.
I retired from the Laboratory in 2004, so there may be some changes in the storage of documents of which I am not aware. Good luck in finding the information that you seek.