[Alex V.]

"Horsepower" is far from synonymous with "towing and hauling" - torque is a different story. Very few truck engines before the most recent generation (say, 2010 and newer?) produce more horsepower than torque. A Duramax diesel from, say, 2003, makes only 360 HP but something over 600 lb.-ft. of torque - current ones are somewhere around the 900 lb.-ft. mark.

Set your sights on about 300 HP/400 tq. with a torque peak between 2,000 and 2,600 RPM and a horsepower peak below 4,500 and it'll tow plenty more than a near-stock 1/2 ton has any business handling or stopping.