I highly doubt its torque steer. Generally torque steer is only a term used for front wheel drive cars with unequal lengh drive shafts.
Could you have torque related steering problems? Probably. I doubt its from your rear axle though. Most of the time, it seems to be related to bump steer.
Try a simple test. Find an empty parking lot. Accelerate hard, without holding onto the steering wheel. If the truck moves straight, and you see the steering wheel move, its steering related, not torque steer.
If you mash on the gas, and you start moving out of line, try the same, except slow on the gas (still with the hands off the wheel. ). If it does the same thing, no matter how quickly you give it gas, then you might have some binding issues with your brakes.
Although I have heard of drag racers claiming that their cars had a bias to move to one side vs the other. Maybe the way the gear is cut? *shrug*.