In regards to '39-'47 trucks, a lot has been said about the differences between 1/2 tons and 1.5 tons(and larger). The general consensus has been that the cabs are the same, hood/grille may be the same but the fenders are definitely bigger. I admit that I thought this to be true also.
Some have read my other thread regarding the multiple trucks and parts I've recently begun collecting. As a result, I have several fenders/hoods/grilles etc. cluttering up my life. I couldn't be happier!
I took an afternoon and did some comparisons of these parts. Here's what I found.

Cabs are the same.