The Bradbury Building is located at 304 South Broadway in downtown Los Angeles. The building is famous for having featured in numerous films, books and television series.
For the 1982 film Blade Runner, it housed J.F. Sebastian's apartment, and its roof was the scene for the famous rooftop chase sequence at the end. The building also featured in Double Indemnity (1944), D.O.A. (1950), M (1951), I, The Jury (1953), The Indestructible Man (1956), Good Neighbor Sam (1964), Chinatown (1974), Avenging Angel (1985), Murphy's Law (1986), Wolf (1994), Disclosure (1994), Lethal Weapon 4 (1998) and (500) Days of Summer (2009).
Here, Pynchon is referring to the 1969 film Marlowe, based on Raymond Chandler's novel The Little Sister, in which the famous private-eye is played by James Garner.