For what it's worth, check out the resto pack information as well. It has a few diagrams that are worthwhile. I'd post the link, but I'm not on the right computer at the moment to find it. I have been in the same boat with my '39. Since the '40 and the '39 are tweener trucks with a lot in common and a lot different any photos you need from mine are yours for the asking. All I have to do is go out an shoot whatever you are looking for. The only major difference is the cab styling and width of the bed between our trucks.
As others have mentioned from the firewall back, the 40 is essentially the same as the 41-46. From the firewall forward, the 40 shares very similar styling to the 39.
Best of luck to you! The 39-40's are the most styling trucks in the entire Chevy lineup. Could I be a bit biased? No, no, no, no, no, no, no, yes....
