400 hp 5.2l vs 5.9l Magnums

I question this. In reality, even with 13% more gear with a 5.2 Liter, WHICH ONE WOULD YOU TOW WITH?
That seems to put the perspective of effective torque.
Technically if both engines have similar hp powerband both should be go to go. But generally you don't want have to spin a work engines wears out quicker but gearing can do a lot look at rock crawlers they can spin the engine at peak power rpm usually decently high at slower than walking speed. Why people like diesel is peak power isn't too far from idle.

While hundreds of pounds of torque isn't NEEDED in an A body, it gratifies results faster, and if you don't have your foot in it to the floor, maybe with less fuel if you baby it (to some degree of diminishing returns).
Torque is basically one powerstroke, hp is all the powerstrokes added up over time "rpm"

A bigger engine may make more per powerstroke "Torque" but smaller engine will have more powerstrokes to add up "rpm*. Which will balance out if making same hp.