* Specific trim level: Different options (like added features, different cabs, etc.) added weight.
* Transmission: Automatic or manual transmissions had different weights.
* Axle ratio: Different ratios affected the weight of the differential assembly.
To find the closest approximation, you would need to consult a 1989 Chevrolet K2500 brochure or owner's manual specific to that model year and engine. Even then, it will likely give a range rather than an exact figure.
You might find some information on online forums dedicated to classic Chevrolet trucks, where owners might share their truck's weight if they have weighed it. However, treat such information with caution as it may not apply to all variations.
