It looks like GMC
has set their sights on dethroning the Ford
Raptor as the ultimate off-road truck. The GMC Sierra All Terrain HD doesn't really have a name that rolls off the tongue quite as readily as the Raptor, but it certainly isn't lacking in capability. GMC took a different route with the engine than that of its rival, going for a 6.6-liter V8 Duramax diesel engine.That means horsepower is slightly lower than the Raptor's, at 397.