As far as I know the the order from smallest to largest throw reduction is 545, Z3 then Z4.
I have the Z4 one, was a straight fit, no bending or other mods required, though I am not sure how it would be in the 320d's.
As far as I recall when fitting the Z3 one the selector rod needs to be bent, I think gizmo has the Z3 one on his 330i.
Karthik, it is pretty easy to get hold of one of these shift levers, just go to the dealers with the part number and order it, but you will probably have to wait a while to get it as not a lot of people buy shift levers :rollsmile:
The old thread about it:
http://www.bmwfanatics.co.za/showthread.php?tid=14494