To the OP: if your Z3 has the M52 engine then most parts will be compatible. The biggest issue is lack of engine space. I'm not too familiar with the Z3 particularly. Check to see which transmission you have. When you find the model of tranny you can find a clutch that will fit. If its the same tranny found in an E36 then you may have an easier time searching for a clutch that is compatible with that model tranny.
Most E36 trannsmissions can handle the increased strain. Their are numerous E36s running Forced Induction. I haven't heard of a transmission failing due to the increase but I'm sure it is possible. With proper maintenance you should be fine.
Now, if you haven't already a good idea could be taking a look at www.realoem.com
. They have a number of parts diagrams available that may help you to visualize the spacing. Try ECS Tunning as they seem to carry a good selection of turbo related components.