what is the difference between the 3800 series II and series III non supercharged?

The UIM is aluminum and the tb is drive by wire.
Edit:
Here are pics of the differences between the upper intake manis:
http://www.conncgp.net/gallery/Project-L26?page=1

What application is the fuel rail for in those photos?

Cheers,

I'm pretty sure it'* just a L36 fuel rail.

I think its a shame they couldn't do more to the engine to make it more powerful. Couldn't they do more to it rather than just slapping on an aluminim intake which frankly should have been done a LONG time ago?

Does anyone happen to know if the UIM to LIM gasket is the same?

That frankly doesn't appear to be too hard to adapt to the Series II throttle body, if so.

The series 2 and 3 make the same HP/TQ IIRC. But it is a shame they couldn't do more to make it more powerful.

This has been done a few times on CGP and talked about on here.(possibly done but I don't remember)
You need to drill and tap a few holes in the L26 UIM, and get a L67 Gen V */c adapter to physically make it work.
But..
You will loose your PVC system since it is external on the L26.
And your IAC valve won't work either.
Also,
Looking at the exit of the L36 TB and the opening of the L26 UIM, you can see they are far from matching. That odd ball oval to circular transistion will hurt flow. A L67 TB will match up closer but may be too big for a run of the mil L36 not to mention different tuning needed.