I like the LED tail lights of the newer models...but not the two different size headlights for the HID lights...

You mean 2004-2009 tail lamps, right? The tail lamps look a lot larger on the later model cars (which would make sense, since the trunks are larger). I don't think they'll bolt up, if that's your aim.

They won't fit, the ones on the X308 are definitley smaller than the X350's.