Hold on, I think I answered my own questions above! I'm guessing rear springs and shocks (Dampers) due to the fact they are stronger as the car is built for four people not two, it's not as though the mounting points are different. These two items (if I did it) are not an issue as I have never in 15 years carried two people in the back (extra weight) so I see no need to change them for carrying only two people. As to gas tank, I can check part numbers on that, and the top yes it would have to be re worked.
I'm still curious about the how the body/windscreen differ which I'm going to look in to more.
Pat