* Engine Size and Type: A small-block Chevy V8 (like a 350) from a '97 is *more likely* to fit in a '90 GMC than a larger engine or a different type (like a diesel). However, even then, there might be minor differences in mounting points.
* Transmission: The transmission must be compatible with both the '97 engine and the '90 truck's drivetrain. A different transmission may require significant modifications.
* Wiring Harness: The engine's wiring harness may not be compatible with the '90 GMC's system. You'll likely need to modify or replace the harness.
* Computer/ECM: The engine control module (ECM) needs to be compatible with the rest of the system. You might need to swap the ECM or do some significant rewiring.
* Exhaust System: The exhaust system may require modification or replacement to fit the new engine.
* Accessories: Power steering, alternator, and other accessories need to be compatible and fit the '90 GMC's setup.
In short, while *possible* with significant work, it's not a simple bolt-in swap. You'll likely need some mechanical expertise, custom fabrication, and potentially a fair bit of time and money to make it work. You should consult a mechanic familiar with these trucks to assess the feasibility and estimate the cost.
