Dear Mr. Gjedrem,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located Central Decimal Files, 1910 - 1963 in the General Records of the Department of State (Record Group 59) that may include files relating to the internal affairs of the Soviet Union. These records are arranged according to the Department of State Decimal Filing Manual. The country number for Russia is 61. We also located National Intelligence Surveys, 1948 - 1972; Reports on the Soviet Union and the Sino-Soviet Bloc , 1947 - 1978; and National Intelligence Estimates and Related Reports and Correspondence, 1950 - 1985 in the Records of the Central Intelligence Agency (Record Group 263) that may include analysis of the internal affairs of the Soviet Union in the final years of Stalin’s life. For more information about these records, please contact the National Archives at College Park - Textual Reference (RDT2) at Archives2reference@nara.gov.
Due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of NARA staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request from RDT2. We apologize for this inconvenience and appreciate your understanding and patience.
Records of the Soviet government are in the custody of the State Archive of the Russian Federation. Additionally, there may be diplomatic and intelligence information concerning the Soviet Union in the national archives of other nations that had an interest in monitoring conditions in the USSR, such as the National Archives of the United Kingdom.
Finally, there are a number of academic institutions dedicated to Russian studies which may be able to advise you in your research. An unofficial list is available on Wikipedia at https://en.wikipedia.org/wiki/List_of_Russian_studies_centers.
We hope this is helpful. Best of luck with your research!