I've been reading this forum anonymously, have finally registered.
I have a SD40VE, wife has a SD9VE. I just bought a 9mm de-mill weapon to shoot cheaper ammo. Received in the package was everything but the frame. I found the slide, barrel, ejector and mag release are the four differences between the .40 & 9mm. I tested this by completely swapping the frames. Within the magazines the followers are different, but that's it.

With the ejector & mag release being different, its more difficult than I expected to switch from .40cal carry to 9mm training.http://smith-wessonforum.com/images/smilies/frown.gif

Thanks