No, a 1989 Chevy S10 4.3L engine will not be a direct bolt-in fit for a 1996 4WD Blazer. While both are 4.3L engines, there are significant differences between the older TBI (throttle body injection) systems used in the 1989 S10 and the later, likely MPI (multi-port injection) system in the 1996 Blazer. This means different engine harnesses, computers, and potentially even different mounts. Furthermore, the accessories (alternator, power steering pump, etc.) may be in different locations.
You could *potentially* adapt it, but it would be a major undertaking requiring significant modification and fabrication, far beyond a simple swap. It's generally easier and more cost-effective to source a 4.3L engine specifically from a similar-year Blazer.
