I would pay attention to weight of said tires. First hand experience made ma aware of that problem, 5 pounds can make a difference. One might not think so, however 5 Ibs. sitting in the cab is different then 5 Ibs. rolling, I'm sure someone here can explain it in scientific terms.
For me it happened when the tire shop accidently installed load "E" instead of my ordered load "C". All of a sudden I has having to downshift on hills I normally gained speed on and taking off from a full stop was painful. Now of course size had some factor in play but that dynamic load was more then I wanted to deal with without new gears.
Goodyear Duratracs were my choice and I am really impressed with them, if I didn't get good years then I would have gotten a set of coopers