Although these are GMC, Chev and GMC were very similar except for the engine and the grill. The prewar one shown is a 41 model and the post war is a 46. The post war had part of the front fenders cut away to save iron because iron was still in short supply right after the war. In mid 1947 Chev came out with the Advanced Design. GMC called it the New design. Mechanically there wasn't much difference, but the cab changed radically.

https://photos.app.goo.gl/ouGNxrqBTSewU8Cf9