are the flywheels of a miata and a 323/protege the same??
 

http://belfabracing.com/index.php?cPath=261_263_374

Found this on belfab...

Are the 1.6 flywheels the same??, and the 1.8 flywheels??

Maybe we can find some cheap lightweight flywheels there...

And clutches?? any interchangabilities?? if not, why?

No - the protege pedestal heights are different. I can't remember all the details, but I had a Protege LX and some 1.8 clutch parts and didn't do the swap because the parts were not exactly the same. That said- I'm running a 1.8 Miata clutch & pp with an 80s 626 flywheel on an FE3 - so it might be able to work with some research and work.