The GZL is very cool! From the EarthCruiser web site listed above.
Looking at the information online, the GZL is offered for Toyota Tacoma and Nissan Frontier. I think the GZL will fit in the Chevrolet Colorado's bed as well.
Looking at overall width, width at wheel wells, height of box, and width at box opening, the Colorado is an inch or two larger than the Tacoma. For example, width between the wheel wells for the Colorado is 44.4 inches, Tacoma 41.5 inches. Height of the box, 20.9 inches vs 19.1 inches. Width of the tailgate opening, 55.5 inches vs 53.4 inches.
The 4x4 crew cab Colorado comes from the factory with a 300+ lb payload advantage over the Tacoma, even when equipped with the 4 cylinder diesel engine that offers 369 ft lb of torque.
Speaking of that diesel engine, over at Fuelly.com, fuel economy for the Colorado diesel is around 24 mpg. The 2016 Tacoma with 3.5L V6 comes in at around 20 mpg. That's a 20% improvement using diesel, which is still less expensive that unleaded regular in most parts of the country. Of course, your mpg results may vary.