It will not direct fit the XR2
You can make a clutch combo that will work, but you have to use a smaller clutch disk size. (miata uses smaller disk) The ONE thing the XR2 transmission has going for it is a large clutch disk
AZGTX is right, get the proper Fidanza flywheel - if you shop around or buy used you can get a deal. I have one in the GTXR2 and one in my red XR2, with a ACT clutch - bulletproof combo.
Personally I kinda prefer the stock flywheel - don't notice much gains from the lighter weight, and makes it tougher to drive especially with a grabby clutch. I only threw it in the red XR2 because I didn't have a good stock flywheel, I was in a pinch - and I had the Fidanza bit on the shelf ready to go