* Small-block V8s: These were likely either a 5.0L (305 cubic inch) or a 5.7L (350 cubic inch). The 350 was more common in heavier duty or higher-trim vans.
* Inline-6: A 4.1L (250 cubic inch) inline-six-cylinder engine was also an option, generally in lower-spec vans.
To know for sure what engine is in *a specific* 1982 Chevy G20, you'd need to check the vehicle's documentation (owner's manual, or a sticker inside the door jamb), or look at the engine itself for an ID tag.