I believe that Series 1 and II clusters are from different manufacturers, and there might be a difficulty with swapping them.
Why not go to a Series 1 Calais cluster, or even HSV. That way you get additional functionality with the change.
I did this swap on both an MY1 and MY12.5 SV6. From my reading, doubledip (on this forum and carmodder) has the ability to do the swap for you in Sydney if you want it enough to pay for it.