As far as I am aware the clutch is either bespoke to the M3W or nobody outside MMC knows which parts bin the components came from. I'm reasonably sure that it's got nothing to do with the MX5/Miata.
I've done some research and it appears that the short M3W flywheel mounting shaft has the same bolt pattern as the Miata uses, at least in that year range up to around '15.
There are race clutches out there for the Miata with light weight aluminium flywheels with stage 1 or 2 pressure plate and disc.
First one I found: $196.95 US Free Shipping
eBay US Miata Flywheel-Clutch Assy 1 Second one: $215 US Free Shipping
eBay US Miata Flywheel-Clutch Assy 2 This might be worth looking into.
I know that there are some kick butt Miata's running lots more hp than the M3W without any major clutch issues.
Good luck.
