Which one of those has good info on the radio truck?
The book from Poland, Opel Blitz, is available in the states, but it is pricey and only covers the truck on the cover. Check out the pictures. https://www.abebooks.com/servlet/BookDetailsPL?bi=13517372501&searchurl=isbn%3D9788389088789%26sortby%3D17
Not sure about the others, here is the write up from the German author. [The Opel Blitz was what the Beetle was for car construction: the benchmark, both in terms of durability and reliability. And like this one, it was launched in the thirties, then ran in gigantic quantities off the line and was still in the fifties the undisputed leader in the class of small trucks with two tons of payload. After the parent company General Motors had decided to introduce a British Bedford instead of lightning in the future, the end had come for the traditional series. What remains are pictures, reports and brochures of this small economic miracle, which find their place in this book by Wolfgang Westerwelle.]
Try typing the vehicle type into their search, found some good info on one of my vehicles.