GMC 2½
definitely
I have read German descriptions from Winter 43/44, full of complains how Soviet troops pushed through mud in LL trucks while their own trucks, Opels etc, got struckt even on the roads, not that there was much difference between cross-country and road in Ukraina in that time during thaw season. Have not time to check the British vehicles but generally US trucks tended to have more powerful engines than European trucks.
Again
a very nice photo, Soren
Juha