Many of today's "1/2 ton" pickups are using stronger frames, heavier suspension components, stronger running gear components, and higher capacity coolling systems than "3/4 ton" pickups of 2000 vintage. This is particularly the case when you buy the "1/2 ton" with the high payload and HD towing packages.
Don't get wrapped up in horsepwer numbers, thats not what determines towing capacity. When you move up into medium-duty trucks with even greater towing capacity, you will find some of the same engines down-rated substantially, for a 100% duty cycle rating, as oppossed to the "maximum I can't make it reach on a dyno" ratings used to sell trucks to buyers looking for bragging rights.
