Im no expert but the end of the diff looks post war and the front wheels. another good and easy way to tell is the back of the cab. the one in this pic is post war and has all those rectangular pressings in it there is guys on this site who know more than me- where are they?
You can also tell from rear wheel hub. On post-war the axle is bolted to the axle with a flange like most "normal" trucks, on wartime its only a center nut. The Opel on the photo also have tha post-war Opel grill shield. The "blitz" disapared after the war.... The doors also have a 90 degrees lower front corner on wartime, but are cut 45 degrees on post-war.