I think that is a really good factory picture. WHS had made some high resolution prints of that image for sale at the IHCC Winter Convention the year it was in Madison. I should have bought one at the time rather than just staring at it. There is some detail I remember that can't be seen at this resolution.
The 2 rail cars in the closest foreground are Farmall Cs. The next car back is International (not Farmall) Super As. Note that both the Cs and Super As are loaded facing alternate directions. Note that the next car farther back and the loaded cars to the very left of the picture are loaded facing one direction. I assume that the ones loaded that way are Cubs, but can't tell from the picture. The tractors on the ground facing the camera, starting with the short rows, are 6 rows of Super As, then 4 rows of Cs. Beyond that I can't tell.
If you follow the rail cars from the foreground around the right side as far as you can see it, then look just a little bit to the left, there is a yellowish blob. Then a bit to the left of it, much nearer the building is another larger yellow blob. The second yellow blob is 3 yellow Cubs. You would need a high-res print to identify them.
The black seat covering would have been cotton duck at that time. A non-padded seat (rarely seen by then) would have been red.