Where is the computer on a 1989 Corvette?

There is no computer in the sense of a standalone, easily identifiable box like a desktop PC in a 1989 Corvette. The "computer" in a 1989 Corvette is the engine control module (ECM), also sometimes called the Powertrain Control Module (PCM). This is a collection of integrated circuits and other electronics embedded within the car's electrical system, often located somewhere under the dash or in the engine compartment (the exact location varied slightly by trim and options). It's not a separate, removable unit like a modern laptop.