B4.2.4. Changes to pre-AACR2 records
With the exception of updating headings to currently valid forms, changes to pre-AACR2 records should be made only in the context of the cataloging code under which the record was created. If it is not possible to make the changes without creating a "hybrid" record, then the record should be converted to AACR2 (See also B3.3.).
It should be noted especially that, for pre-AACR2 records, the bibliographic description description is based on the latest available issue rather than on the earliest.
See also: