Dear Mr. Plants,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located a series titled Command Chronologies and Related Documentation, 4/1962 - 6/1987 in the Records of the U.S. Marine Corps (Record Group 127) that is the main body of records of Marine operations in Vietnam and includes 494 digitized files units pertaining to the 1st Marine Regiment. You also may view unit information via the Records of War website.
In addition, we located the series titled “Records Primarily Relating to the Vietnam War and Cold War Operations and Training, 1953 - 1993” in Record Group 127 that they may contain records of interest to you at the division or higher levels. Plus, we located the series“ Vietnam Operations Reports, , 3/1965 - 6/1971” in the Records of the Office of the Chief of Naval Operations (Record Group 38) that include operations of the Fleet Marine Force, Pacific during Vietnam.
We hope this information is helpful. Best of luck with your research!