These big and gnarly Ward LaFrance “Heavy Wrecking Trucks” were built during WW2 to provide a variety of services out in the field, and not just towing broken down Sherman tanks or 6×6 trucks. With their large cranes, they actually were used more for field repairs: swapping out major components on field equipment, including artillery, tanks, trucks and all other equipment. The crane could lift a tank turret, engine, or barrel on a field artillery piece, as well as anything else a heavy and powerful 6×6 truck and crane could be employed to do.
Many of these trucks were passed on to NATO and other countries, where they were often in service until the 1990s. But they were typically very well maintained, and of course not used much after the war, so collectors have found some in quite good condition in ought various countries, although there is the cost of repatriating them.
I found a very good write-up of one that was bought in Italy, and is still being used by the owner as a mobile crane in his WW2 military equipment restoration work, like lifting out the heavy 9-cylinder engines out of a Sherman tank. Makes for good reading, if you want to know more about these.
Here’s one at work in Korea, lifting a tank turret.
These trucks were powered by a large Continental ohv gasoline engine (2.5 mpg). The crane was all mechanical (gears and cables) as hydraulic hoses were of course more at risk of getting taken out by a stray bullet.