The wheels should fit fine - but those tires are seriously too short (diameter). Check out the Miata.net Tire Size Calculator
- compared to the stock 225/45-18s, your 215/35s are 2.1 inches shorter!!! (23.9 vs. 26.0) That's 8% shorter, and you'll throw off your speedometer by 5 mph at 60 mph. Not to mention, shortening the diameter by 2 inches means you'll lose 1 inch of ground clearance.
I'd recommend against using those tires on an RX-8.