Can someone school me on the differences between the 39-40 models?

[metalman]

Unless someone comes up with some obscure factory documentation to demonstrate that some late production cars came with early release parts it's not likely. It's not hard to switch hubs and drums, and a lot can happen in 70 years.

Learn somthing every day! I just assumned mine was stock, rest of the car was. First 39 I've had and never paid that close attention to them before.

 

[Uncle Bob]

I remember hearing stories many moons ago from then old timers (it's all relative) that it wasn't too uncommon with older Fords for guys to swap parts to make the car appear to be a newer model, or gain advantages of later part updates. So they would put '40 seal beam buckets and bezels on a '39 instead of some cheesy looking aftermarket conversion. Or more extreme, swap a '34 grille and hood to a '33, or a '36 front clip to a '35.

 

[Hamtown Al]

I bought a 35 3W in early 80s that had received a 36 front clip in the 40s. It worked for me!!