* Physically fits: The engine might physically squeeze into the engine bay, but require extensive modifications to the firewall, hood, suspension, etc.
* Fit with reasonable modifications: Meaning significant but manageable modifications.
* Bolt-in swap: Meaning minimal to no modifications.
A direct bolt-in swap is highly unlikely for anything significantly larger than the stock engine. Even a simple swap requires dealing with things like engine mounts, exhaust, wiring, and cooling systems.
Realistically, larger engines from other GM platforms (like some V6s from the same era) might be plausible with considerable fabrication and modification. However, even these swaps would present major challenges. You'd likely need custom engine mounts, exhaust, possibly a modified transmission, and likely extensive bodywork to accommodate the larger engine.
Trying to shoehorn in a much larger V8 or something similar would be an extremely involved and likely impractical project requiring significant fabrication skills, custom parts, and potentially weakening the car's structural integrity.
In short, while some larger engines *might* be squeezed in, it's far more realistic to consider swaps within the same or similar GM platform to minimize the amount of custom fabrication required. You'll need to research specific engine swaps (e.g., searching for "1989 Cavalier Z24 engine swap" online) and look at forums and communities dedicated to this type of work to see what others have successfully done.
