GMC had factory installed auxiliary transmissions, but I doubt that a 49 Chev would be have been a factory installation. It doesn't look like the drag axle was factory either. My guess is that someone built a truck to haul more than it was designed to haul, which was very common. And it was also common, that if your engine was underpowered, you got more gears. Salvage yards were full of wrecked larger trucks, and it was common to buy an auxiliary out of a larger truck and put it in a 2 ton.
