Will a Chevrolet Corsica engine fit in Blazer?

No, a Chevrolet Corsica engine will almost certainly not fit in a Chevrolet Blazer, especially without significant modifications. The Corsica was a compact car, and the Blazer was a significantly larger SUV. The engine bays, engine mounts, and associated components are completely different. Even if you could somehow physically cram the engine in, adapting the transmission, driveshaft, wiring harness, and other systems would be a monumental and likely impractical task.