Here's my own custom Sierra. Description has been edited so that there is less confusion.
Some of you may notice its got a...Solid Front Axle!!! Its got a lot of other stuff as well, such as a different styled rear bed (it's simply a 3500 SRW bed but with really thick fenders), and a (I'm fantasizing a little) Duramax/Allison 7-speed that outputs 620 hp/1225 lb-ft. torque which is also biodiesel capable. This truck's meant to tow big loads while having good off-road capabilities to get it to most places normal duallies can't go.
Overall, I tried practicing with multiple colors to make the drawing more realistic. I think it turned out alright. I probably should have spent more time on the grained aluminum parts of the truck (the grille, lower bumper, roof) since a lot of people might think it's chrome. Also, some people on another site mentioned the size of the mirrors. The truth is, those mirrors are actually the same size as the stock ones. They just seem small because of the sheer largeness of the truck overall.
The same people on the other website complained it looks too much like an F-450. My goal wasn't to make it look like a Ford. The grille design is actually from an old Sierra design I drew six years ago (so in a way, that blocky design is actually my idea ). Again, this is my own CUSTOM truck, not an interpretation of a future vehicle.