The black truck pictured is a 54. 54 was the first year for the curved 1 piece windshield. That windshield was used for the 54 model year, and until the month of May, just passed 1/2 through, the 1955 model year, when the cab was reconfigured and the door posts were stood straight up and the windshields wrapped around to the door posts. The wrap-a-around windshields went unchanged through the 1960 model year. The 1st truck pictured on this thread is a late 55 or 56 cab. You can clearly see the differences between the 2 windshields.

That 54 & early 55 windshield was hard to find, and expensive new, over 15 years ago. New versions were over $500, 15 years ago. I have to wonder if new 54 windshields are even available new any more.

The blue truck Bigdad posted, just before the 2 pictures of the black truck is a 53. Other then the shape of the grill opening, and grill, and the box fenders, the 48-53 trucks are very similar. The 53 would have been the last year for the split windshields. You can also see the differences in the nose piece between the hood and the headlights, on the 48-53, that area rises up, on the 54-56 it dips down. Harder to notice is the differences in the height of the hood, to top of fender, when comparing the 53 to the 54-56 trucks. The 48-53 hood is a couple of inches higher then the fender tops on the 54-56 trucks. I also believe the roof height on the 48-53 trucks are higher then the 54-56 and newer trucks are. Gene