Dear Mr. Linn,
Thank you for posting your request on History Hub!
The following two file units are for 1972:
Creator: Department of Defense. Pacific Command. U.S. Military Assistance Command Vietnam. Office of Civil Operations and Rural Development Support. CORDS Military Region 3. Office of Program Coordination. Phung Hoang Division. 1971-3/29/1973, from the Series: General Records, 1967 - 1972, Record Group 472: Records of the U.S. Forces in Southeast Asia.
Creator: Department of Defense. Pacific Command. U.S. Military Assistance Command Vietnam. Office of Civil Operations and Rural Development Support. CORDS Military Region 1. Advisory Team 19 (Quang Tri Province Advisory Team). 9/15/1968-3/29/1973, from the Series: Administrative and Operational Records, 5/1967 - 3/1973, Record Group 472: Records of the U.S. Forces in Southeast Asia
Additional information below is provided by Reference Archivist Martin Gedra:
For the Phoenix Program, Ashes to Ashes by Dale Andrate at CMH may be a good starting point. He used NARA records. It may be able to list series which deal with possible changes near the end of military involvement.
Looking at records of the 525th may be the better approach, but there may be access issues. Just looking in the National Archives Catalog, the following jump out:
https://catalog.archives.gov/id/5719198 has two officer debriefs in Boxes 276 and 286 dealing with the 525th. Unclear, though, is what years.
https://catalog.archives.gov/id/5716811 (also unclear of the years) has records in Box 7 and deals with the UAASA, which makes me think that they could be useful.
https://catalog.archives.gov/id/5928020 will be the series with MI units. Boxes 5 and 6 have history files, but some of the others (issuances in Box 15?) The Operational Reports-Lessons Learned in Boxes 31-32 typically are quarterly summaries, so that may be a good starting point too.
The MACV annual command summaries may provide an overarching overview of what is happening and changes from year to year.
For access to these file units please contact the National Archives at College Park - Textual Reference (RDT2) via email at email@example.com.
We hope this is helpful. Best of luck with your research!