McCarthy was being fed info from J. Edgar Hoover, who did have access to the Venona transcripts. I don't know if he was given the identities of known spies, but he was sent after Hoover's bureaucratic rivals.

McCarthy was not after spies as in "trained intelligence workers", he was trying to ferret out a certain subset of his political opponents, whose goals he imagined to be aligned with those of the USSR. Nowdays, of course, most people consider his activities to be anti-American.