https://archive.org/details/sherlockholmes_otr
Posted at the link are 52 shows from the Mutual Broadcasting System radio program starring Basil Rathbone as Sherlock Holmes and Nigel Bruce as Dr. Watson.
The show was sponsored in 1939-40 by Grove's Bromo Quinine and later enjoyed an extended run as The New Adventures of Sherlock Holmes under the sponsorship of Petri Wines. These recordings are of varying quality with most in the good to very good sound range. The files have been tagged with the most accurate information available and each file name begins with the original broadcast air date. ——internet archive
And
Here is a list of all of the actors who played Sherlock Holmes in Old Time Radio (OTR). All worth listening to, all fine actors for the role.