The Foundation archive is at the Getty Research Institute, Special Collections. The archive contains plans for virtually every Lautner building, and photographs of most (although the foundation does not have the rights to many of the photographs). These materials can be copied or loaned under certain circumstances.
Start here. Click on the link to the “finding aid” on the right side of the page.
Search to see if there are plans or photographs of the buildings you are interested in. If you can get to the Getty you can request permission to see what is available. For more info on borrowing materials from the Getty: