I have a few questions:

1. Can anyone tell me what size flywheels the different Z cars have?
   
2. Also, how interchangeable are they?
   
3. How do you determine what flywheel you should install (i.e. based upon engine block, tranny model, etc)?
   
4. And how do you determine what clutch you need to buy (i.e. based upon engine block, tranny, flywheel, etc)?
   

Generally, coupes have 225mm flywheels, 2+2s have 240mm. Different clutches, too.

Choose clutch based on Flywheel size. You can use a 240mm Flywheel in a coupe if you want. I would not use the 225mm flywheel on a 2+2.