If you look here you will find an interesting table.
http://www.onlyz3.com/en/prod_all.html
It will show you the chassis number ranges for each variant of Z3. A variant being Roadster or Coupe, Engine Size, Transmission, Market (USA or EUROPE), LHD or RHD.
So for each of these variants you will be able to see how close to the end of the chassis number range you are. Which you can probably fairly assume was issued in serial order.
But what you probably won't ever find out is even if you are the last number in that range, where you fall across all ranges/variants.
I have one of the last 25 3.0 RHD manuals produced. Kind of interesting but ultimately it will change nothing!