More power is always a good thing, but a more powerful vehicle that's broken is worse than not having a truck at all, because you have to spend resources fixing it.

And that's what the advantage of the Studebaker US6 and other similar vehicles sent to the USSR via lend-lease was: they were almost bulletproof. The engine in the US6, a straight-six 5.2L thing, was a conservative beast. It may have been down on horsepower, but it was long on reliability. It was easy to maintain, easy to repair, could run on 70 octane gasoline (try that with your car today!), and could probably be dropped off a cliff and still work.

But even the famous "Deuce-and-a-half" truck used by the US throughout the war only had 91hp, the "Go-Devil" engine used by the Willys MB Jeep turned out 60hp, and the famous amphibious DUKW had 94hp. 86hp put the US6's engine in the same ballpark. In comparison, many British trucks had horsepower numbers in the low 70s.

So there you have it: a relatively normal engine built for reliability and pulling power rather than speed that would be easy to repair if it ever broke.

Most American vehicles before 1950 favored big, burly, low RPM, high torque drivetrains. The concept being to get you out of trouble on unpaved, unimproved roads. A contemporary Cadillac of the era, a 1939 Fleetwood sixty special only turned at 700 rpm and made 135hp. The monobloc V8 in the Cadillac was also used in M3 Stuart tanks! So you can get the idea that the large displacement engines of the era were VERY capable. 322ci spread over 8 beefy pistons could pull stumps out of your backyard!

(Source : "Cadillac, it came out fighting!" By Jeffrey Shively)