towing is a lot about gearing in both trans and rear ends, just cause a motor makes "X" amount of HP on paper, the real deal tends to be most all motors make HP at rpms NO one in the right mind will be running or towing at
them 5.7 Hemi numbers sound way better than real world driving use will ever get you near them!
even if you look at Ram/Dodge tow ratings on Half tons, as to, say Ford/chevy, its a huge difference, dodge/ram just doesn't have much in towing LBS in 1/2 tons
get into a 3/4 ton and trucks can handle more towing lbs, BUT trucks also get a lot heavier in actually weight of just the truck alone, (most 3/4 ton trucks weigh about 1500 lbs more than there 1/2 ton of like truck)
so them same motors, well, have less HP to LB ratings , so how much better do you think they do on them HP/Torque numbers
its back to different gearing that helps off set things
just like adding larger tires to an atv, you have to change gearing to meet the new needs of asking from same motor Hp output!
and there is a HUGE Difference in towing on flat land as to any place with hills or altitude , all motors loose Hp as you go higher in things
its why diesel's rule the towing world, all the more so one's with turbo's, NO Hp loss, and they make power at rpms you actually drive at/tow at.
a gas motors need way more RPM"S to make like Hp numbers and torque, and thus use more fuel to do so!
on flat land again, about any truck of decent weight can tow things 150 % better than the same truck will in rolling hills, here where I am at, every 5-10 miles you change 500-2000 ft in elevation, its all UP hill down hill, to go any where, and all my gas trucks ended a LOT of rpms to get up and over every hill, thus sucked at MPG"S as you were always screaming things when towing blowing out any good MPG numbers LOL
same truck on flat land was night and day different in towing!