Rear axle rotational torque is what the 'torque' in torque tube is all about. The forward thrust of the axle housing is transfered to the frame through the springs as in any rear drive car since the tube is free to slide fore and aft at the front end. The big advantage is the dampening of the torque attempting to raise the front of the axle housing on acceleration. The long torque tube provides excellent leverage to control this. An open driveline vehicle suffers from spring wrap and resulting axle hop due to this unless some sort of control in used, bars or pinion snubber.
Of course the ujoints in stovebolt torque tubes are too small to take a lot of punishment from big motors. But, I have seen a lot of pickups with v8s and stock drivelines in years past. The v8 clutch housing will bolt up to the pickup transmission but you have to be creative with motor mounts.
I think Buick was the only major brand to use torque tubes with fairly large V8s, in the mid to late 50s and they worked really well.
